mn88473: fix chip id check on probe

mn88473: fix chip id check on probe

commit d930b5b5bf122a61952cfebabb1e618682a2631a upstream.

A register used to identify chip during probe was overwritten during
firmware download and due to that later probe's for warm chip were
failing. Detect chip from the another register, which is located on
different register bank 2.

Fixes: 7908fad99a6c ("[media] mn88473: finalize driver")
Signed-off-by: Antti Palosaari <crope@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>