drm/amd/display: Insert smu busy status before sending another request

[why]
Need to check if result register is busy before sending another request

[how]
Call method to check if result register is busy

Reviewed-by: Charlene Liu <Charlene.Liu@amd.com>
Acked-by: Tom Chung <chiahsuan.chung@amd.com>
Signed-off-by: Oliver Logush <oliver.logush@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>