[PATCH] net/9p/usbg: allow building as standalone module

[Dominique Martinet <asmadeus@codewreck.org>]

There is no reason only the usbg transport would not be its own module,
so make it tristate.

In particular, this fixes a couple of issues the current bool had:
- trans_usbg was apparently not compiled at all when NET_9P=m
- the workaround added in commit 2193ede180dd ("net/9p/usbg: fix
CONFIG_USB_GADGET dependency") became redundant because a tristate item
cannot be built-in when its dependency is a module, so we can depend on
USB_GADGET "normally" again.

Signed-off-by: Dominique Martinet <asmadeus@codewreck.org>
Cc: Michael Grzeschik <m.grzeschik@pengutronix.de>
Link: https://lkml.kernel.org/r/ZzhWRPDNwu225NWz@codewreck.org
---
 net/9p/Kconfig | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/9p/Kconfig b/net/9p/Kconfig
index ee967fd25312..22f8c167845d 100644
--- a/net/9p/Kconfig
+++ b/net/9p/Kconfig
@@ -41,8 +41,8 @@ config NET_9P_XEN
 	  two Xen domains.
 
 config NET_9P_USBG
-	bool "9P USB Gadget Transport"
-	depends on USB_GADGET=y || USB_GADGET=NET_9P
+	tristate "9P USB Gadget Transport"
+	depends on USB_GADGET
 	select CONFIGFS_FS
 	select USB_LIBCOMPOSITE
 	help
-- 
2.46.1