drm/amd/pm: Add VCN reset support check capability

drm/amd/pm: Add VCN reset support check capability

This change introduces infrastructure to check whether VCN reset
is supported by the SMU firmware. Key changes include:

1. Added new functions to query VCN reset support:
   - amdgpu_dpm_reset_vcn_is_supported()
   - smu_reset_vcn_is_supported()
   - pptable_funcs.reset_vcn_is_supported callback

2. Implemented proper locking in the DPM layer with mutex protection

3. Maintained consistency with existing SDMA reset support checks

The new capability allows callers to check for VCN reset support
before attempting the operation, preventing unnecessary attempts
on unsupported platforms.

v2: clean up debug info(Alex)

Suggested-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Ruili Ji <ruiliji2@amd.com>
Signed-off-by: Jesse Zhang <Jesse.Zhang@amd.com>
Reviewed-by: Lijo Lazar <lijo.lazar@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>