drm/i915/gtt: Allow >= 4GB offsets in X86_32

Similar to commit c44ef60e437019b8ca1dab8b4d2e8761fd4ce1e9 ("drm/i915/gtt:
Allow >= 4GB sizes for vm"), i915_gem_obj_offset and i915_gem_obj_ggtt_offset
return an unsigned long, which in only 4-bytes long in 32-bit kernels.

Change return type (and other related offset variables) to u64.

Since Global GTT is always limited to 4GB, this change would not be required
in i915_gem_obj_ggtt_offset, but this is done for consistency.

v2: Remove unnecessary offset variable in do_pin, as we already have
    vma->node.start (Chris).
    Update GGTT offset too (Tvrtko).

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Signed-off-by: Michel Thierry <michel.thierry@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index cefb6e9..6b85338 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -2977,13 +2977,11 @@
 struct dma_buf *i915_gem_prime_export(struct drm_device *dev,
 				struct drm_gem_object *gem_obj, int flags);
 
-unsigned long
-i915_gem_obj_ggtt_offset_view(struct drm_i915_gem_object *o,
-			      const struct i915_ggtt_view *view);
-unsigned long
-i915_gem_obj_offset(struct drm_i915_gem_object *o,
-		    struct i915_address_space *vm);
-static inline unsigned long
+u64 i915_gem_obj_ggtt_offset_view(struct drm_i915_gem_object *o,
+				  const struct i915_ggtt_view *view);
+u64 i915_gem_obj_offset(struct drm_i915_gem_object *o,
+			struct i915_address_space *vm);
+static inline u64
 i915_gem_obj_ggtt_offset(struct drm_i915_gem_object *o)
 {
 	return i915_gem_obj_ggtt_offset_view(o, &i915_ggtt_view_normal);