media: dvb: Add check on sp8870_readreg return

The function sp8870_readreg returns a negative value when i2c_transfer
fails so properly check for this and return the error if it happens.

Cc: Sean Young <sean@mess.org>
Cc: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Alaa Emad <alaaemadhossney.ae@gmail.com>
Link: https://lore.kernel.org/r/20210503115736.2104747-60-gregkh@linuxfoundation.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/media/dvb-frontends/sp8870.c

@@ -280,7 +280,9 @@ static int sp8870_set_frontend_parameters(struct dvb_frontend *fe)
 	sp8870_writereg(state, 0xc05, reg0xc05);
 
 	// read status reg in order to clear pending irqs
-	sp8870_readreg(state, 0x200);
+	err = sp8870_readreg(state, 0x200);
+	if (err < 0)
+		return err;
 
 	// system controller start
 	sp8870_microcontroller_start(state);