drm/amd/display: re-enable wait in pipelock, but add timeout

commit 627f75d18910b287472593a4a2c41de9a386f5a2 upstream.

Removing this causes hangs in some games, so re-add it, but add
a timeout so we don't hang while switching flip types.

Bug: https://bugzilla.kernel.org/show_bug.cgi?id=205169
Bug: https://bugs.freedesktop.org/show_bug.cgi?id=112266


Reviewed-by: Harry Wentland <harry.wentland@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>