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

commit ab1dd996 upstream.

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>

drivers/staging/vt6656/rf.c

@@ -769,6 +769,9 @@ BYTE    byPwr = pDevice->byCCKPwr;
         return TRUE;
     }
 
+	if (uCH == 0)
+		return -EINVAL;
+
     switch (uRATE) {
     case RATE_1M:
     case RATE_2M: