drm/i915/userptr: Kill user_size limit check

GTT was only 32b and its max value is 4GB. In order to allow objects
bigger than 4GB in 48b PPGTT, i915_gem_userptr_ioctl we could check
against max 48b range (1ULL << 48).

But since the check no longer applies, just kill the limit.

v2: Use the default ctx to infer the ppgtt max size (Akash).
v3: Just kill the limit, it was only there for early detection of an
error when used for execbuffer (Chris).

Cc: Akash Goel <akash.goel@intel.com>
Reviewed-by: NChris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: NMichel Thierry <michel.thierry@intel.com>
Reviewed-by: NAkash Goel <akash.goel@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_gem_userptr.c

@@ -813,7 +813,6 @@ static const struct drm_i915_gem_object_ops i915_gem_userptr_ops = {
 int
 i915_gem_userptr_ioctl(struct drm_device *dev, void *data, struct drm_file *file)
 {
-	struct drm_i915_private *dev_priv = dev->dev_private;
 	struct drm_i915_gem_userptr *args = data;
 	struct drm_i915_gem_object *obj;
 	int ret;
@@ -826,9 +825,6 @@ i915_gem_userptr_ioctl(struct drm_device *dev, void *data, struct drm_file *file
 	if (offset_in_page(args->user_ptr | args->user_size))
 		return -EINVAL;
 
-	if (args->user_size > dev_priv->gtt.base.total)
-		return -E2BIG;
-
 	if (!access_ok(args->flags & I915_USERPTR_READ_ONLY ? VERIFY_READ : VERIFY_WRITE,
 		       (char __user *)(unsigned long)args->user_ptr, args->user_size))
 		return -EFAULT;