drm/amdgpu: Restrict bootloader wait to SMUv13.0.6

Restrict the wait for boot loader steady state only to SMUv13.0.6. For
older SOCs, ASIC init has a longer wait period and that takes care.

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