[media] tuner-xs2028.c: fix sparse warnings

drivers/media/tuners/tuner-xc2028.c:575:24: warning: cast to restricted __le16
drivers/media/tuners/tuner-xc2028.c:686:21: warning: cast to restricted __le16

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Reviewed-by: Michael Krufky <mkrufky@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>