drm/amdgpu/vce: Move firmware load to amdgpu_vce_early_init

drm/amdgpu/vce: Move firmware load to amdgpu_vce_early_init

Try to load the VCE firmware at early_init.

When the correct firmware is not found, return -ENOENT.
This way, the driver initialization will complete even
without VCE, and the GPU will be functional, albeit
without video encoding capabilities.

This is necessary because we are planning to add support
for the VCE1, and AMD hasn't yet publised the correct
firmware for this version. So we need to anticipate that
users will try to boot amdgpu on SI GPUs without the
correct VCE1 firmware present on their system.

Signed-off-by: Timur Kristóf <timur.kristof@gmail.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Leo Liu <leo.liu@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>