staging: lustre: ptlrpc: lproc_ptlrpc.c - fix dereferenceing user space buffer

- this fixes sparse warning for directly deferencing user space buffer

drivers/staging/lustre/lustre/ptlrpc/lproc_ptlrpc.c:652:33: warning: incorrect type in argument 2 (different address spaces)
drivers/staging/lustre/lustre/ptlrpc/lproc_ptlrpc.c:652:33: expected void const [noderef] <asn:1>*from
drivers/staging/lustre/lustre/ptlrpc/lproc_ptlrpc.c:652:33: got char const *buffer

Signed-off-by: Anil Belur <[e-mail]>
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/staging/lustre/lustre/ptlrpc/lproc_ptlrpc.c

···
  * if the optional token is omitted, the operation is performed on both the
  * regular and high-priority (if the service has one) NRS head.
  */
-static ssize_t ptlrpc_lprocfs_nrs_seq_write(struct file *file, const char *buffer,
+static ssize_t ptlrpc_lprocfs_nrs_seq_write(struct file *file,
+					const char __user *buffer,
 					size_t count, loff_t *off)
 {
 	struct ptlrpc_service *svc = ((struct seq_file *)file->private_data)->private;