[media] wl128x-radio really depends on TI_ST

All other drivers using the TI_ST infrastructure use
'depends on' for this symbol, and it makes no sense
to only enable that if CONFIG_NET is enable, because
the radio driver also depends on CONFIG_NET itself:

ERROR: "skb_queue_purge" [drivers/media/radio/wl128x/fm_drv.ko] undefined!
ERROR: "skb_push" [drivers/media/radio/wl128x/fm_drv.ko] undefined!
ERROR: "skb_pull" [drivers/media/radio/wl128x/fm_drv.ko] undefined!

Making the driver dependency explicit solves randconfig
build problems and makes it more obvious to the reader.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>