rpmsg: char: add CONFIG_NET dependency

Without CONFIG_NET, we get a build failure for the new driver:

ERROR: "skb_queue_tail" [drivers/rpmsg/rpmsg_char.ko] undefined!
ERROR: "skb_put" [drivers/rpmsg/rpmsg_char.ko] undefined!
ERROR: "__alloc_skb" [drivers/rpmsg/rpmsg_char.ko] undefined!
ERROR: "kfree_skb" [drivers/rpmsg/rpmsg_char.ko] undefined!
ERROR: "skb_dequeue" [drivers/rpmsg/rpmsg_char.ko] undefined!

This adds a dependency so we don't try to build the broken configuration.

Fixes: c0cdc19f ("rpmsg: Driver for user space endpoint interface")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>

drivers/rpmsg/Kconfig

@@ -7,6 +7,7 @@ config RPMSG
 config RPMSG_CHAR
 	tristate "RPMSG device interface"
 	depends on RPMSG
+	depends on NET
 	help
 	  Say Y here to export rpmsg endpoints as device files, usually found
 	  in /dev. They make it possible for user-space programs to send and