drm/amdgpu/smu_v11_0: Correct behavior of restoring default tables (v2)

Previously, the syfs functionality for restoring the default powerplay
table was sourcing it's information from the currently-staged powerplay
table.

This patch adds a step to cache the first overdrive table that we see on
boot, so that it can be used later to "restore" the powerplay table

v2: sqaush my original with Matt's fix

Bug: https://gitlab.freedesktop.org/drm/amd/issues/1020
Signed-off-by: Matt Coffin <mcoffin13@gmail.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org # 5.5.x