[PATCH] proc: fix missing reference of mm

The defconfig build of blackfin was failing with the error:
fs/proc/task_nommu.c: In function 'is_stack':
fs/proc/task_nommu.c:132:28: error: 'mm' undeclared (first use in this function)

While reverting /proc/<pid>/maps [stack:TID] annotation a reference to
mm was missed.

Fixes: e87d4fd02f40 ("proc: revert /proc/<pid>/maps [stack:TID] annotation")
CC: Johannes Weiner <[email protected]>
Signed-off-by: Sudip Mukherjee <sudip-ofJRbWXBVFamYgehrs7/[email protected]>
---

The build log of blackfin defconfig is at:
https://travis-ci.org/sudipm-mukherjee/parport/jobs/103757285

 fs/proc/task_nommu.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/fs/proc/task_nommu.c b/fs/proc/task_nommu.c
index 60ab72e..faacb0c 100644
--- a/fs/proc/task_nommu.c
+++ b/fs/proc/task_nommu.c
@@ -126,6 +126,7 @@ unsigned long task_statm(struct mm_struct *mm,
 static int is_stack(struct proc_maps_private *priv,
 		    struct vm_area_struct *vma, int is_pid)
 {
+	struct mm_struct *mm = vma->vm_mm;
 	int stack = 0;
 
 	if (is_pid) {
-- 
1.9.1