drm/i915: Introduce intel_psr.c

No functional changes. Just cleaning and reorganizing it.

v2: Rebase it puting it to begin of psr rework. This helps to blame easily
at least latest changes.

Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/intel_frontbuffer.c b/drivers/gpu/drm/i915/intel_frontbuffer.c
index 58cf2e6..79f6d72 100644
--- a/drivers/gpu/drm/i915/intel_frontbuffer.c
+++ b/drivers/gpu/drm/i915/intel_frontbuffer.c
@@ -156,7 +156,7 @@
 
 	intel_mark_fb_busy(dev, obj->frontbuffer_bits, ring);
 
-	intel_edp_psr_invalidate(dev, obj->frontbuffer_bits);
+	intel_psr_invalidate(dev, obj->frontbuffer_bits);
 }
 
 /**
@@ -182,7 +182,7 @@
 
 	intel_mark_fb_busy(dev, frontbuffer_bits, NULL);
 
-	intel_edp_psr_flush(dev, frontbuffer_bits);
+	intel_psr_flush(dev, frontbuffer_bits);
 
 	/*
 	 * FIXME: Unconditional fbc flushing here is a rather gross hack and