drm/amd/pp: enable power limit increase in OD mode

drm/amd/pp: enable power limit increase in OD mode

OverDrive mode allows users to increase the maximum SCLK and MCLK
frequencies beyond the default on the GPU. However, this may not
results in large performance gains if the GPU then runs into its TDP
power limit. This patch adds the capability to increase the power
limit of a GPU above its default maximum.

This is only allowed when overdrive is enabled in the ppfeaturemask,
since this is an overdrive feature. The TDPODLimit value from the
VBIOS describes how how much higher the TDP should be allowed to go
over its default, in percentage.

v2: Moved dereference of hwmgr to after its validity check

Signed-off-by: Joseph Greathouse <Joseph.Greathouse@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>