drm/amdgpu/soc21: update VCN 4 max HEVC encoding resolution

Update the maximum resolution reported for HEVC encoding on VCN 4
devices to reflect its 8K encoding capability.

Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/3159


Signed-off-by: Thong <thong.thai@amd.com>
Reviewed-by: Ruijing Dong <ruijing.dong@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>