GFX/UVD PG

[Tom St Denis]

This is another resend but this time re-organized from scratch so there
is no revert patch in here.

These patches enable GFX and static UVD PG for Stoney and Carrizo.
UVD PG support is enabled in both DPM and Powerplay.  Powerplay is corrected
to set the clock after ungating power as well as to not power down before
the UVD core is initialized.

All tested on an AM4 Carrizo and a Gardenia Stoney.