drm/amd/powerplay/smu7_hwmgr: replace blocking delay with non-blocking

This driver currently contains a repeated 500ms blocking delay call
which causes frequent major buffer underruns in PulseAudio. This patch
fixes this issue by replacing the blocking delay with a non-blocking
sleep call.

Signed-off-by: Yrjan Skrimstad <yrjan@skrimstad.net>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>