drm/i915: Drop expectations of VM_IO from our GGTT mmappings

We don't really want to use VM_IO for our GGTT mmaps (it implies that
the mmap contains memory mapped registers, which we do not expose) yet I
overzealously added it to an assert just because that's how we always
had setup the vma.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Abdiel Janulgue <abdiel.janulgue@linux.intel.com>
Reviewed-by: Abdiel Janulgue <abdiel.janulgue@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190807094128.9993-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_mm.c

@@ -63,9 +63,8 @@ int remap_io_mapping(struct vm_area_struct *vma,
 	struct remap_pfn r;
 	int err;
 
-	GEM_BUG_ON((vma->vm_flags &
-		    (VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP)) !=
-		   (VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP));
+#define EXPECTED_FLAGS (VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP)
+	GEM_BUG_ON((vma->vm_flags & EXPECTED_FLAGS) != EXPECTED_FLAGS);
 
 	/* We rely on prevalidation of the io-mapping to skip track_pfn(). */
 	r.mm = vma->vm_mm;