drm/amd/display: Only revalidate bandwidth on medium and fast updates

commit 6eb3cf2e upstream.

[Why]
Changes that are fast don't require updating DLG parameters making
this call unnecessary. Considering this is an expensive call it should
not be done on every flip.

DML touches clocks, p-state support, DLG params and a few other DC
internal flags and these aren't expected during fast. A hang has been
reported with this change when called on every flip which suggests that
modifying these fields is not recommended behavior on fast updates.

[How]
Guard the validation to only happen if update type isn't FAST.

Bug: https://gitlab.freedesktop.org/drm/amd/-/issues/1191
Fixes: a24eaa5c

 ("drm/amd/display: Revalidate bandwidth before commiting DC updates")
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Roman Li <Roman.Li@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>