staging: ti-st: depends on RFKILL

staging: ti-st: depends on RFKILL

Fix build errors.  st_kim.c uses rfkill*() interfaces, so it
should depend on RFKILL.

st_kim.c:(.text+0x291b21): undefined reference to `rfkill_unregister'
st_kim.c:(.text+0x291b31): undefined reference to `rfkill_destroy'
st_kim.c:(.text+0x291d8a): undefined reference to `rfkill_alloc'
st_kim.c:(.text+0x291db9): undefined reference to `rfkill_init_sw_state'
st_kim.c:(.text+0x291dc9): undefined reference to `rfkill_register'
st_kim.c:(.text+0x291e07): undefined reference to `rfkill_unregister'
(.text+0x291e85): undefined reference to `rfkill_set_hw_state'
(.text+0x292072): undefined reference to `rfkill_set_hw_state'
(.text+0x2920e1): undefined reference to `rfkill_set_hw_state

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>