[media] coda: add coda_estimate_sizeimage and use it in set_defaults

Call coda_estimate_sizeimage from both try_fmt and set_defaults to
avoid this v4l2-compliance warning on the h.264 decoder video device:

    G_FMT:     1920x1088, 32315559, 1, 1920, 1048576, 3, 0, 0, feedcafe
    TRY/S_FMT: 1920x1088, 32315559, 1, 1920, 3133440, 3, 0, 0, feedcafe
    fail: v4l2-test-formats.cpp(948): Video Capture: S_FMT(G_FMT) != G_FMT

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>