[media] coda: add coda_write_base helper

Add a helper function that writes a vb2_buffer's Y, Cb, and
Cr plane base addresses of into three consecutive registers.
This moves common code out of coda-bit.c.

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Kamil Debski <k.debski@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>