vt6655: RFbSetPower fix missing rate RATE_12M

commit 40c8790b upstream.

When the driver sets this rate a power of zero value is set causing
data flow stoppage until another rate is tried.
Signed-off-by: Malcolm Priestley <tvboxspy@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>

drivers/staging/vt6655/rf.c

@@ -923,6 +923,7 @@ bool RFbSetPower(
 		break;
 	case RATE_6M:
 	case RATE_9M:
+	case RATE_12M:
 	case RATE_18M:
 		byPwr = pDevice->abyOFDMPwrTbl[uCH];
 		if (pDevice->byRFType == RF_UW2452)