[media] b2c2: Mismatch in config ifdefs for SkystarS2

Compilation warning issued by kbuild test robot:
>> drivers/media/common/b2c2/flexcop-fe-tuner.c:31:12: warning: 'flexcop_fe_request_firmware' defined but not used [-Wunused-function]
    static int flexcop_fe_request_firmware(struct dvb_frontend *fe,

This patch fixes a mismatch in Kconfig define checks. One had a
check for just CX24120, the other is checking for both CX24120
and ISL6421.
Signed-off-by: NJemma Denson <jdenson@gmail.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@osg.samsung.com>

drivers/media/common/b2c2/flexcop-fe-tuner.c

@@ -27,7 +27,7 @@
 #define FE_SUPPORTED(fe) (defined(CONFIG_DVB_##fe) || \
 	(defined(CONFIG_DVB_##fe##_MODULE) && defined(MODULE)))
 
-#if FE_SUPPORTED(BCM3510) || FE_SUPPORTED(CX24120)
+#if FE_SUPPORTED(BCM3510) || (FE_SUPPORTED(CX24120) && FE_SUPPORTED(ISL6421))
 static int flexcop_fe_request_firmware(struct dvb_frontend *fe,
 	const struct firmware **fw, char *name)
 {