staging: ST_BT depends on RFKILL

Fix kconfig unmet dependency warning:

warning: (ST_BT && STAGING && !STAGING_EXCLUDE_BUILD && BT) selects TI_ST which has unmet direct dependencies (RFKILL)

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