[why]
when an update programming sequence requires both
front end and back end pipe to be updated synchronously,
a global update lock needs to be set to ensure that
we don't get a frame with only front end update but
not the back end update.

[how]
setup global lock parameters on enable_stream_timing.
enable global lock when pipe_control_lock_global is called.
disable global lock when pipe_control_lock is called.
Signed-off-by: Wenjing Liu <Wenjing.Liu@amd.com>
Reviewed-by: Tony Cheng <Tony.Cheng@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>