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_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index 7a0ddee..68e7caf 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -300,9 +300,6 @@
 	drm_helper_hpd_irq_event(dev);
 }
 
-/* defined intel_pm.c */
-extern spinlock_t mchdev_lock;
-
 static void ironlake_handle_rps_change(struct drm_device *dev)
 {
 	drm_i915_private_t *dev_priv = dev->dev_private;
@@ -936,7 +933,7 @@
 			offset += src->stolen->start;
 			offset += i << PAGE_SHIFT;
 
-			memcpy_fromio(d, (void *)offset, PAGE_SIZE);
+			memcpy_fromio(d, (void __iomem *) offset, PAGE_SIZE);
 		} else {
 			struct page *page;
 			void *s;