First round of fixes for 3.18.
- Use gart for DMA ring tests to avoid caching issues with HDP
- SI dpm stability fixes
- Performance stabilization fixes
- misc other things

* 'drm-fixes-3.18' of git://people.freedesktop.org/~agd5f/linux:
  drm/radeon: reduce sparse false positive warnings
  drm/radeon: fix vm page table block size calculation
  drm/ttm: Don't evict BOs outside of the requested placement range
  drm/ttm: Don't skip fpfn check if lpfn is 0 in ttm_bo_mem_compat
  drm/radeon: use gart memory for DMA ring tests
  drm/radeon: fix speaker allocation setup
  drm/radeon: initialize sadb to NULL in the audio code
  Revert "drm/radeon/dpm: drop clk/voltage dependency filters for SI"
  Revert "drm/radeon: drop btc_get_max_clock_from_voltage_dependency_table"