staging: vt6656: [BUG] out of bound array reference in RFbSetPower.

Calling RFbSetPower with uCH zero value will cause out of bound array reference.

This causes 64 bit kernels to oops on boot.

Note: Driver does not function on 64 bit kernels and should be
blacklisted on them.

Signed-off-by: Malcolm Priestley <tvboxspy@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>