[media] s5p-mfc: Update scratch buffer size for VP8 encoder

Scratch buffer size updated for vp8 encoding as per
the latest v7 firmware. As the new macro increases the
scratch buffer size, it is backward compatible with the older
firmware too.

Signed-off-by: Kiran AVND <avnd.kiran@samsung.com>
Signed-off-by: Arun Kumar K <arun.kk@samsung.com>
Signed-off-by: Kamil Debski <k.debski@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>