wrappers for ->i_mutex access

parallel to mutex_{lock,unlock,trylock,is_locked,lock_nested},
inode_foo(inode) being mutex_foo(&inode->i_mutex).

Please, use those for access to ->i_mutex; over the coming cycle
->i_mutex will become rwsem, with ->lookup() done with it held
only shared.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c
index 92e6726..a939f5e 100644
--- a/fs/proc/kcore.c
+++ b/fs/proc/kcore.c
@@ -552,9 +552,9 @@
 	if (kcore_need_update)
 		kcore_update_ram();
 	if (i_size_read(inode) != proc_root_kcore->size) {
-		mutex_lock(&inode->i_mutex);
+		inode_lock(inode);
 		i_size_write(inode, proc_root_kcore->size);
-		mutex_unlock(&inode->i_mutex);
+		inode_unlock(inode);
 	}
 	return 0;
 }