drm/amdgpu: validate GEM_CREATE domain combinations

drm/amdgpu: validate GEM_CREATE domain combinations

AMDGPU_GEM_CREATE checked domain bits against AMDGPU_GEM_DOMAIN_MASK,
but did not validate domain combinations. Userspace could combine
CPU|GTT|VRAM with DOORBELL, GDS, GWS, or OA, making
amdgpu_bo_placement_from_domain() exceed AMDGPU_BO_MAX_PLACEMENTS and
hit BUG_ON().

Allow combinations only within CPU/GTT/VRAM, and require non-CPU/GTT/
VRAM domains to be specified one at a time. Return -EINVAL for invalid
combinations in amdgpu_gem_create_ioctl().

v2: Rename helper from amdgpu_gem_domain_valid() to
    amdgpu_gem_are_domains_valid() (Christian)

Signed-off-by: Candice Li <candice.li@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>