radeon_hd: Implement initial DP encoder service

* Used on older chipsets. Untested.
radeon_hd: Fix Spread Spectrum clock decimal place

* As 104Mhz is stores as 10400 on atombios,
  and 104000 everywhere else... this conversion
  was going the wrong direction.
* Shrink the stored value to 10Khz units to properly
  compare to the AtomBIOS value