drm/amdgpu: Add AQUIRE_MEM PACKET3 fields defintion

Add this for gfx10 and gfx9.

v2: Fix identation

Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky@amd.com>
Reviewed-by: Luben Tuikov <luben.tuikov@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>