staging: csr: add INET dependancy

Randy noticed that with CONFIG_INET turned off, the following build
errors happen:
	ERROR: "register_inetaddr_notifier" [drivers/staging/csr/csr_wifi.ko] undefined!
	ERROR: "unregister_inetaddr_notifier" [drivers/staging/csr/csr_wifi.ko] undefined!

Reported-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>