drm/amd/display: Optimize bandwidth on following fast update

commit 34316c1e upstream.

[Why]
The current call to optimize_bandwidth never occurs because flip is
always pending from the FULL and FAST updates.

[How]
Optimize on the following flip when it's a FAST update and we know we
aren't going to be modifying the clocks again.

Reviewed-by: Bhawanpreet Lakha <bhawanpreet.lakha@amd.com>
Acked-by: Mikita Lipski <mikita.lipski@amd.com>
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: Mario Limonciello <Mario.Limonciello@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>