drm/amd/pm/smu11: BACO is supported when it's in BACO state

Return true early if ASIC is in BACO state already, no need
to talk to SMU. It can fix the issue that driver was not
calling BACO exit at all in runtime pm resume, and a timing
issue leading to a PCI AER error happened eventually.

Fixes: 8795e182 ("PCI/portdrv: Don't disable AER reporting in get_port_device_capability()")
Suggested-by: Lijo Lazar <lijo.lazar@amd.com>
Signed-off-by: Guchun Chen <guchun.chen@amd.com>
Reviewed-by: Lijo Lazar <lijo.lazar@amd.com>
Reviewed-by: Evan Quan <evan.quan@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>