drm: drop setting vm_file to filp

Talking to Al Viro on irc, we can see no possible reason for doing
this, the upper mmap code does it. The code has been there since
first import into drm tree I can find.

Al tracked down this as a requirement pre 2.3.51 hasn't been needed since.

Acked-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/drm_gem.c b/drivers/gpu/drm/drm_gem.c
index f8625e2..3ebe3c8 100644
--- a/drivers/gpu/drm/drm_gem.c
+++ b/drivers/gpu/drm/drm_gem.c
@@ -700,7 +700,6 @@
 	 */
 	drm_gem_object_reference(obj);
 
-	vma->vm_file = filp;	/* Needed for drm_vm_open() */
 	drm_vm_open_locked(vma);
 
 out_unlock:
diff --git a/drivers/gpu/drm/drm_vm.c b/drivers/gpu/drm/drm_vm.c
index 8c03eaf..55cd615 100644
--- a/drivers/gpu/drm/drm_vm.c
+++ b/drivers/gpu/drm/drm_vm.c
@@ -519,7 +519,6 @@
 	vma->vm_flags |= VM_RESERVED;	/* Don't swap */
 	vma->vm_flags |= VM_DONTEXPAND;
 
-	vma->vm_file = filp;	/* Needed for drm_vm_open() */
 	drm_vm_open_locked(vma);
 	return 0;
 }
@@ -671,7 +670,6 @@
 	vma->vm_flags |= VM_RESERVED;	/* Don't swap */
 	vma->vm_flags |= VM_DONTEXPAND;
 
-	vma->vm_file = filp;	/* Needed for drm_vm_open() */
 	drm_vm_open_locked(vma);
 	return 0;
 }
diff --git a/drivers/gpu/drm/exynos/exynos_drm_gem.c b/drivers/gpu/drm/exynos/exynos_drm_gem.c
index 025abb3..6545251 100644
--- a/drivers/gpu/drm/exynos/exynos_drm_gem.c
+++ b/drivers/gpu/drm/exynos/exynos_drm_gem.c
@@ -208,7 +208,6 @@
 
 	/* in case of direct mapping, always having non-cachable attribute */
 	vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
-	vma->vm_file = filp;
 
 	vm_size = vma->vm_end - vma->vm_start;
 	/*
diff --git a/drivers/gpu/drm/i810/i810_dma.c b/drivers/gpu/drm/i810/i810_dma.c
index 64a989e..2c8a60c 100644
--- a/drivers/gpu/drm/i810/i810_dma.c
+++ b/drivers/gpu/drm/i810/i810_dma.c
@@ -99,7 +99,6 @@
 	buf_priv = buf->dev_private;
 
 	vma->vm_flags |= (VM_IO | VM_DONTCOPY);
-	vma->vm_file = filp;
 
 	buf_priv->currently_mapped = I810_BUF_MAPPED;