[media] s5p-mfc: limit the size of the CPB

The CPB size is limited by the hardware. Add this limit to the s_fmt.

Signed-off-by: panpan liu <panpan1.liu@samsung.com>
Signed-off-by: Kamil Debski <k.debski@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>