[PATCH v4l-utils] treewide: fix discards 'const' qualifier from pointer

[Rudi Heitbaum <rudi@heitbaum.com>]

For ISO C23, the functions strchr, strrchr, and strstr that return
pointers into their input arrays now have definitions as macros that
return a pointer to a const-qualified type when the input argument is
a pointer to a const-qualified type.

Update to const type for variable, as returned string is only used in
comparisons which const can be used.

fixes:
    ../lib/libdvbv5/dvb-dev-local.c:220:19: warning: assignment discards 'const' qualifier from pointer target type [-Wdiscarded-qualifiers]
      220 |                 p = strstr(pci_dev, "0x");
          |                   ^
    ../lib/libdvbv5/dvb-dev-local.c:224:19: warning: assignment discards 'const' qualifier from pointer target type [-Wdiscarded-qualifiers]
      224 |                 p = strstr(pci_vend, "0x");
          |                   ^
    ../utils/libmedia_dev/get_media_devices.c: In function 'get_associated_device':
    ../utils/libmedia_dev/get_media_devices.c:459:19: warning: assignment discards 'const' qualifier from pointer target type [-Wdiscarded-qualifiers]
      459 |                 p = strrchr(seek_device, '/');
          |                   ^
    ../utils/ir-ctl/ir-ctl.c: In function 'read_scancode':
    ../utils/ir-ctl/ir-ctl.c:530:19: warning: initialization discards 'const' qualifier from pointer target type [-Wdiscarded-qualifiers]
      530 |         char *p = strchr(name, ':');
          |                   ^~~~~~

Signed-off-by: Rudi Heitbaum <rudi@heitbaum.com>
---
 lib/libdvbv5/dvb-dev-local.c           | 3 +--
 utils/ir-ctl/ir-ctl.c                  | 2 +-
 utils/libmedia_dev/get_media_devices.c | 3 ++-
 3 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/lib/libdvbv5/dvb-dev-local.c b/lib/libdvbv5/dvb-dev-local.c
index ea511471..b89a6c87 100644
--- a/lib/libdvbv5/dvb-dev-local.c
+++ b/lib/libdvbv5/dvb-dev-local.c
@@ -208,8 +208,7 @@ static int handle_device_change(struct dvb_device_priv *dvb,
 
 	/* Get optional per-bus fields associated with the device parent */
 	if (!strcmp(bus_type, "pci")) {
-		const char *pci_dev, *pci_vend;
-		char *p;
+		const char *p, *pci_dev, *pci_vend;
 
 		pci_dev = udev_device_get_sysattr_value(parent, "subsystem_device");
 		pci_vend = udev_device_get_sysattr_value(parent, "subsystem_vendor");
diff --git a/utils/ir-ctl/ir-ctl.c b/utils/ir-ctl/ir-ctl.c
index 8600fbe6..d2ff77e4 100644
--- a/utils/ir-ctl/ir-ctl.c
+++ b/utils/ir-ctl/ir-ctl.c
@@ -527,7 +527,7 @@ static struct send *read_scancode(const char *name)
 	struct send *f;
 	unsigned scancode;
 	char *pstr;
-	char *p = strchr(name, ':');
+	const char *p = strchr(name, ':');
 
 	if (!p) {
 		fprintf(stderr, _("error: scancode '%s' must be in protocol:scancode format\n"), name);
diff --git a/utils/libmedia_dev/get_media_devices.c b/utils/libmedia_dev/get_media_devices.c
index 21920867..28efb658 100644
--- a/utils/libmedia_dev/get_media_devices.c
+++ b/utils/libmedia_dev/get_media_devices.c
@@ -452,7 +452,8 @@ const char *get_associated_device(void *opaque,
 	struct media_devices *md = opaque;
 	struct media_device_entry *md_ptr = md->md_entry;
 	int i, found = 0;
-	char *prev, *p;
+	const char *p;
+	char *prev;
 
 	if (seek_type != NONE && seek_device[0]) {
 		/* Get just the device name */
-- 
2.51.0