[media] s5p-fimc: Remove V4L2_FL_LOCK_ALL_FOPS flag

This patch adds locking for open(), close(), poll() and mmap()
file operations in the driver as a follow up to the changes
done in commit 5126f259
"v4l2-dev: add flag to have the core lock all file operations".

Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>