[media] pulse8-cec: some small fixes

Fix some small things:
    - clean up setup function
    - use MSGEND instead of 0xfe
    - don't assign "return value" from cec_phys_addr to err,
      it has return type void.

Signed-off-by: Johan Fjeldtvedt <jaffe1@gmail.com>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>