drm/i915: combine all small integers into one single bitfield

This saves a whooping 7 dwords. Zero functional changes. Because
some of the refcounts are rather tightly calculated, I've put
BUG_ONs in the code to check for overflows.

Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Eric Anholt <eric@anholt.net>
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index c51495f..bf70355 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2247,6 +2247,9 @@
 	struct inode *inode;
 	struct page *page;
 
+	BUG_ON(obj_priv->pages_refcount
+			== DRM_I915_GEM_OBJECT_MAX_PAGES_REFCOUNT);
+
 	if (obj_priv->pages_refcount++ != 0)
 		return 0;
 
@@ -4156,6 +4159,8 @@
 	struct drm_i915_gem_object *obj_priv = to_intel_bo(obj);
 	int ret;
 
+	BUG_ON(obj_priv->pin_count == DRM_I915_GEM_OBJECT_MAX_PIN_COUNT);
+
 	i915_verify_inactive(dev, __FILE__, __LINE__);
 	if (obj_priv->gtt_space == NULL) {
 		ret = i915_gem_object_bind_to_gtt(obj, alignment);