drm/amd/display: Use current_state when checking old_pipe subvp type

drm/amd/display: Use current_state when checking old_pipe subvp type

[Description]
When checking the subvp type of the previous state we must
pass in current_state to the interface instead of context
otherwise we will get the wrong result.

Reviewed-by: Samson Tam <samson.tam@amd.com>
Acked-by: Zaeem Mohamed <zaeem.mohamed@amd.com>
Signed-off-by: Alvin Lee <alvin.lee2@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>