drm/i915: fixup sparse warnings

- __iomem where there is none (I love how we mix these things up).
- Use gfp_t instead of an other plain type.
- Unconfuse one place about enum pipe vs enum transcoder - for the pch
  transcoder we actually use the pipe enum. Fixup the other cases
  where we assign the pipe to the cpu transcoder with explicit casts.
- Declare the mch_lock properly in a header.

There is still a decent mess in intel_bios.c about __iomem, but heck,
this is x86 and we're allowed to do that.

Makes-sparse-happy: Chris Wilson <chris@chris-wilson.co.uk>
[danvet: Use a space after the cast consistently and fix up the
newly-added cast in i915_irq.c to properly use __iomem.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index 58e6676..ce60506 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -546,11 +546,11 @@
 	struct drm_device *dev = node->minor->dev;
 	drm_i915_private_t *dev_priv = dev->dev_private;
 	struct intel_ring_buffer *ring;
-	const volatile u32 __iomem *hws;
+	const u32 *hws;
 	int i;
 
 	ring = &dev_priv->ring[(uintptr_t)node->info_ent->data];
-	hws = (volatile u32 __iomem *)ring->status_page.page_addr;
+	hws = ring->status_page.page_addr;
 	if (hws == NULL)
 		return 0;