drm/amdkfd: Add domain parameter to alloc kernel BO

drm/amdkfd: Add domain parameter to alloc kernel BO

To allocate kernel BO from VRAM domain for MQD in the following patch.
No functional change because kernel BO allocate all from GTT domain.

Rename amdgpu_amdkfd_alloc_gtt_mem to amdgpu_amdkfd_alloc_kernel_mem
Rename amdgpu_amdkfd_free_gtt_mem to amdgpu_amdkfd_free_kernel_mem
Rename mem_kfd_mem_obj gtt_mem to mem

Signed-off-by: Philip Yang <Philip.Yang@amd.com>
Reviewed-by: Kent Russell <kent.russell@amd.com>
Reviewed-by: Felix Kuehling <felix.kuehling@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>