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/Makefile b/drivers/gpu/drm/i915/Makefile
index 891e584..e4083e4 100644
--- a/drivers/gpu/drm/i915/Makefile
+++ b/drivers/gpu/drm/i915/Makefile
@@ -51,6 +51,7 @@
 	  intel_frontbuffer.o \
 	  intel_modes.o \
 	  intel_overlay.o \
+	  intel_psr.o \
 	  intel_sideband.o \
 	  intel_sprite.o
 i915-$(CONFIG_ACPI)		+= intel_acpi.o intel_opregion.o