media: hantro: Auto generate the AXI ID to avoid conflicts

The AXI ID is an AXI bus configuration for improve bus performance.
If read and write operations use different IDs the operations can be
paralleled, whereas when they have the same ID the operations will be
serialized. Right now, the write ID is fixed to 0 but we can set it to
0xff to get auto generated IDs to avoid possible conflicts.

This change has no functional changes, but seems reasonable to let the
hardware to autogenerate the ID instead of hardcoding in software.

Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Signed-off-by: Benjamin Gaignard <benjamin.gaignard@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>