[media] coda: fix job_ready debug reporting for bitstream decoding

Clarify whether job_ready returns false because the context is on hold, waiting
for new input buffers, whether there are not enough input buffers to fill two
into the bitstream, or whether there is not enough data in the bitstream buffer
for the bitstream reader hardware to read a whole frame.

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>