drm/amd/pm: Add debug bit for smu pool allocation

In certain cases, it's desirable to avoid PMFW log transactions to
system memory. Add a mask bit to decide whether to allocate smu pool in
device memory or system memory.

Signed-off-by: Lijo Lazar <lijo.lazar@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>