drm/amdgpu: cleanup SA inti and fini(v2)

should use bo_create_kernel instead of split to two
function that create and pin the SA bo

issue:
before this patch, there are DMAR read error in host
side when running SRIOV test, the DMAR address dropped
in the range of SA bo.

fix:
after this cleanups of SA init and fini, above DMAR
eror gone.

v2:
keep sa_bo's fini instead of suspend, to keep
reporting error

Signed-off-by: Monk Liu <Monk.Liu@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>