misc i915 fixes.
* tag 'drm-intel-next-fixes-2014-12-17' of git://anongit.freedesktop.org/drm-intel:
drm/i915: Disable PSMI sleep messages on all rings around context switches
drm/i915: Force the CS stall for invalidate flushes
drm/i915: Invalidate media caches on gen7
drm/i915: sanitize RPS resetting during GPU reset
drm/i915: move RPS PM_IER enabling to gen6_enable_rps_interrupts
drm/i915: vlv: fix IRQ masking when uninstalling interrupts