drm/amd/display: Implement workaround for writing to OTG_PIXEL_RATE_DIV register

commit 74fa4c81 upstream.

[Why and How]
Current implementation requires FPGA builds to take a different
code path from DCN32 to write to OTG_PIXEL_RATE_DIV. Now that
we have a workaround to write to OTG_PIXEL_RATE_DIV register without
blanking display on hotplug on DCN32, we can allow the code paths for
FPGA to be exactly the same allowing for more consistent
testing.

Reviewed-by: Alvin Lee <Alvin.Lee2@amd.com>
Acked-by: Qingqing Zhuo <qingqing.zhuo@amd.com>
Signed-off-by: Saaem Rizvi <SyedSaaem.Rizvi@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: "Limonciello, Mario" <mario.limonciello@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>