media: adv7604: prevent underflow condition when reporting colorspace

Currently, adv76xx_log_status() reads some date using
io_read() which may return negative values. The current logic
doesn't check such errors, causing colorspace to be reported
on a wrong way at adv76xx_log_status(), as reported by Coverity.

If I/O error happens there, print a different message, instead
of reporting bogus messages to userspace.

Fixes: 54450f59 ("[media] adv7604: driver for the Analog Devices ADV7604 video decoder")
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Reviewed-by: Hans Verkuil <hverkuil@xs4all.nl>