media: mtk-vpu: load vpu firmware from the new location

mt8173 VPU firmware has been moved to a sub-folder of
linux-firmware, so load vpu-fw from the new location first,
if it fails, then from the old one.

Signed-off-by: Rui Wang <gtk_ruiwang@mediatek.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>