NFS: remove redundant __private attribute from nfs_page_class

The nfs_page_class tracepoint uses a pointer for the 'req' field marked
with the __private attribute. This causes Sparse to complain about
dereferencing a private pointer within the trace ring buffer context,
specifically during the TP_fast_assign() operation.

This fixes a Sparse warning introduced in commit b6ef079 ("nfs:
more in-depth tracing of writepage events") by removing the redundant
__private attribute from the 'req' field.

Reviewed-by: Benjamin Coddington <bcodding@hammerspace.com>
Signed-off-by: Sean Chang <seanwascoding@gmail.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>

Author: Sean Chang

fs/nfs/nfstrace.h

@@ -1496,7 +1496,7 @@ DECLARE_EVENT_CLASS(nfs_page_class,
 			__field(dev_t, dev)
 			__field(u32, fhandle)
 			__field(u64, fileid)
-			__field(const struct nfs_page *__private, req)
+			__field(const struct nfs_page *, req)
 			__field(loff_t, offset)
 			__field(unsigned int, count)
 			__field(unsigned long, flags)