[media] mt2063: fix sparse warnings

[media] mt2063: fix sparse warnings

drivers/media/tuners/mt2063.c:1238:56: warning: cast truncates bits from constant value (ffffff0f becomes f)
drivers/media/tuners/mt2063.c:1313:62: warning: cast truncates bits from constant value (ffffff7f becomes 7f)
drivers/media/tuners/mt2063.c:1321:62: warning: cast truncates bits from constant value (ffffff7f becomes 7f)

Cast to u8 is unnecessary.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>