[U-Boot] [PATCH] cmd: mtd: fix compilation warning for help when SYS_LONGHELP=n

[Quentin Schulz <quentin.schulz@bootlin.com>]

cmd/mtd.c:447:13: warning: ‘mtd_help_text’ defined but not used [-Wunused-variable]
static char mtd_help_text[] =
            ^~~~~~~~~~~~~

When SYS_LONGHELP is not defined. After looking at how other commands
work, we should surround the whole help text (even its declaration) with
an #ifdef CONFIG_SYS_LONGHELP, since it's compiled out when calling
_CMD_HELP[1] on the help text variable argument to U_BOOT_CMD.

[1] https://elixir.bootlin.com/u-boot/latest/source/include/command.h#L181

Signed-off-by: Quentin Schulz <quentin.schulz@bootlin.com>
---
 cmd/mtd.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/cmd/mtd.c b/cmd/mtd.c
index 6142223984..361813a4a1 100644
--- a/cmd/mtd.c
+++ b/cmd/mtd.c
@@ -444,8 +444,8 @@ static int do_mtd(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 	return CMD_RET_SUCCESS;
 }
 
-static char mtd_help_text[] =
 #ifdef CONFIG_SYS_LONGHELP
+static char mtd_help_text[] =
 	"- generic operations on memory technology devices\n\n"
 	"mtd list\n"
 	"mtd read[.raw][.oob]                  <name> <addr> [<off> [<size>]]\n"
@@ -466,8 +466,7 @@ static char mtd_help_text[] =
 	"\t\t* must be a multiple of a block for erase\n"
 	"\t\t* must be a multiple of a page otherwise (special case: default is a page with dump)\n"
 	"\n"
-	"The .dontskipff option forces writing empty pages, don't use it if unsure.\n"
+	"The .dontskipff option forces writing empty pages, don't use it if unsure.\n";
 #endif
-	"";
 
 U_BOOT_CMD(mtd, 10, 1, do_mtd, "MTD utils", mtd_help_text);
-- 
2.17.1