drm/amd/display: Revert W/A for hard hangs on DCN20/DCN21

The WA from commit 2a50edbf ("drm/amd/display: Apply w/a for hard hang
on HPD") and commit 1bd3bc74

 ("drm/amd/display: Extend w/a for hard
hang on HPD to dcn20") causes a regression in s0ix where the system will
fail to resume properly on many laptops.  Pull the workarounds out to
avoid that s0ix regression in the common case.  This HPD hang happens with
an external device in special circumstances and a new W/A will need to be
developed for this in the future.

Cc: stable@vger.kernel.org
Cc: Qingqing Zhuo <qingqing.zhuo@amd.com>
Reported-by: Scott Bruce <smbruce@gmail.com>
Reported-by: Chris Hixon <linux-kernel-bugs@hixontech.com>
Reported-by:  <spasswolf@web.de>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=215436
Link: https://gitlab.freedesktop.org/drm/amd/-/issues/1821
Link: https://gitlab.freedesktop.org/drm/amd/-/issues/1852
Fixes: 2a50edbf ("drm/amd/display: Apply w/a for hard hang on HPD")
Fixes: 1bd3bc74

 ("drm/amd/display: Extend w/a for hard hang on HPD to dcn20")
Reviewed-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>