drm/amd/display: Force watermark value propagation

[Why]
The HUBBUB watermark registers are in an area that cannot be power
gated, but the HUBP copies of the watermark values are in areas that can
be power gated. When we power on a pipe, it will not automatically take
the HUBBUB values, we need to force propagation by writing to a
watermark register.

[How]
 - new HUBBUB function to re-write current value in a WM register
 - touch WM register after enabling the plane in program_pipe

Signed-off-by: Joshua Aberback <joshua.aberback@amd.com>
Reviewed-by: Jun Lei <Jun.Lei@amd.com>
Acked-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>