media: adv7842: Avoid possible out-of-bounds array accesses in adv7842_cp_log_status()

In the Linux kernel, the following vulnerability has been resolved:

media: adv7842: Avoid possible out-of-bounds array accesses in adv7842_cp_log_status()

It's possible for cp_read() and hdmi_read() to return -EIO. Those

values are further used as indexes for accessing arrays.

Fix that by checking return values where it's needed.

Found by Linux Verification Center (linuxtesting.org) with SVACE.