media: zr364xx: remove redundant assigmnent to idx, clean up code

The variable cable_type is being initialized with a value that
is never read and is being re-assigned a little later on. Replace
the redundant initializtion with the assignment that occurs a little
later. Also initialize frm too rather than have a later assignment.

Addresses-Coverity: ("Unused value")

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>