media: bdisp: remove redundant assignment to pix

Pointer pix is being initialized to a value and a little later
being assigned the same value again. Remove the initial assignment to
avoid a duplicate assignment. Cleans up the clang warning:

drivers/media/platform/sti/bdisp/bdisp-v4l2.c:726:26: warning: Value
stored to 'pix' during its initialization is never read

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>