drm/amdgpu: add mmhub support for aldebaran (v3)

v1: dupilcate mmhub_v1_7.c from mmhub_v1_0.c because
mmhub register address for aldebaran is different
from existing asics (Le)
v2: switch to latest mmhub_v9_4_2 register headers (Hawking)
v3: squash in init VM_L2_CNTL3 default value for mmhub v1_7

Signed-off-by: Le Ma <le.ma@amd.com>
Signed-off-by: Kevin Wang <kevin1.wang@amd.com>
Reviewed-by: Hawking Zhang <Hawking.Zhang@amd.com>
Acked-by: Evan Quan <evan.quan@amd.com>
Signed-off-by: Hawking Zhang <Hawking.Zhang@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>