drm/amdgpu: reduce the full gpu access time in amdgpu_device_init.

drm/amdgpu: reduce the full gpu access time in amdgpu_device_init.

[Why]
function "devm_memremap_pages" in function "kgd2kfd_init_zone_device",
sometimes cost too much time.

[How]
move the function "kgd2kfd_init_zone_device"
after release full gpu access(amdgpu_virt_release_full_gpu).

v2:
improve the coding style.

Signed-off-by: chong li <chongli2@amd.com>
Reviewed-by: Emily Deng <Emily.Deng@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>