[media] s5p-fimc: Fix V4L2_PIX_FMT_RGB565X description

Remove V4L2_MBUS_FMT_RGB565_2X8_BE media code entry as
camera interface supports only packed YUYV formats.

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>