media: s5p-mfc: Fix in register read and write for H264

[ Upstream commit 06710cd5 ]

Few of the H264 encoder registers written were not getting reflected
since the read values were not stored and getting overwritten.

Fixes: 6a9c6f68

 ("[media] s5p-mfc: Add variants to access mfc registers")

Cc: stable@vger.kernel.org
Cc: linux-fsd@tesla.com
Signed-off-by: Smitha T Murthy <smitha.t@samsung.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Sasha Levin <sashal@kernel.org>