[media] si2168: Small typo fix (SI2157 -> SI2168)

Signed-off-by: NOlli Salonen <olli.salonen@iki.fi>
Reviewed-by: NAntti Palosaari <crope@iki.fi>
Signed-off-by: NAntti Palosaari <crope@iki.fi>
Signed-off-by: NMauro Carvalho Chehab <m.chehab@samsung.com>

drivers/media/dvb-frontends/si2168_priv.h

@@ -36,9 +36,9 @@ struct si2168 {
 };
 
 /* firmare command struct */
-#define SI2157_ARGLEN      30
+#define SI2168_ARGLEN      30
 struct si2168_cmd {
-	u8 args[SI2157_ARGLEN];
+	u8 args[SI2168_ARGLEN];
 	unsigned wlen;
 	unsigned rlen;
 };