drm/amd/display: Remove dependency on pipe->plane for immedaite flip status

[Why]
dcn20_apply_ctx_for_surface can be called with 0 planes, which means we
should blank the display. In this case when we get down to
dcn20_setup_gsl_group_as_lock, pipe_ctx->plane_state is NULL, but we don't
check for it. However, this function is only called by
dcn20_pipe_control_lock, and in that function we alraedy have a local for
the immediate flip status, which is what we care about in the plane state.

[How]
 - pass in immediate flip status as parameter

Signed-off-by: Joshua Aberback <joshua.aberback@amd.com>
Reviewed-by: Krunoslav Kovac <Krunoslav.Kovac@amd.com>
Acked-by: Leo Li <sunpeng.li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>