i915: Add and use pr_fmt and pr_<level>

Use a more current logging style.  Ensure that appropriate
logging messages are prefixed with "i915: ".

Convert printks to pr_<level>.  Align arguments.

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/intel_opregion.c b/drivers/gpu/drm/i915/intel_opregion.c
index 289140b..34929ae 100644
--- a/drivers/gpu/drm/i915/intel_opregion.c
+++ b/drivers/gpu/drm/i915/intel_opregion.c
@@ -25,6 +25,8 @@
  *
  */
 
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
 #include <linux/acpi.h>
 #include <linux/acpi_io.h>
 #include <acpi/video.h>
@@ -355,7 +357,7 @@
 	}
 
 	if (!acpi_video_bus) {
-		printk(KERN_WARNING "No ACPI video bus found\n");
+		pr_warn("No ACPI video bus found\n");
 		return;
 	}