drm/amd/display: use udelay rather than fsleep

drm/amd/display: use udelay rather than fsleep

[ Upstream commit 1d66c3f2b8c0b5c51f3f4fe29b362c9851190c5a ]

This function can be called from an atomic context so we can't use
fsleep().

Fixes: 01f60348d8fb ("drm/amd/display: Fix 'failed to blank crtc!'")
Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/4549
Cc: Wen Chen <Wen.Chen3@amd.com>
Cc: Fangzhi Zuo <jerry.zuo@amd.com>
Cc: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Cc: Harry Wentland <harry.wentland@amd.com>
Reviewed-by: Harry Wentland <harry.wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 27e4dc2c0543fd1808cc52bd888ee1e0533c4a2e)
Signed-off-by: Sasha Levin <sashal@kernel.org>