debugfs: Add debugfs_create_u64()

I went to use this the other day, only to find it didn't exist.

It's a straight copy of the debugfs u32 code, then s/u32/u64/. A quick
test shows it seems to be working.

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

include/linux/debugfs.h

diff --git a/include/linux/debugfs.h b/include/linux/debugfs.h
index 9fa0983..5a9c495 100644
--- a/include/linux/debugfs.h
+++ b/include/linux/debugfs.h
@@ -44,6 +44,8 @@
 				  struct dentry *parent, u16 *value);
 struct dentry *debugfs_create_u32(const char *name, mode_t mode,
 				  struct dentry *parent, u32 *value);
+struct dentry *debugfs_create_u64(const char *name, mode_t mode,
+				  struct dentry *parent, u64 *value);
 struct dentry *debugfs_create_bool(const char *name, mode_t mode,
 				  struct dentry *parent, u32 *value);
 
@@ -104,6 +106,13 @@
 	return ERR_PTR(-ENODEV);
 }
 
+static inline struct dentry *debugfs_create_u64(const char *name, mode_t mode,
+						struct dentry *parent,
+						u64 *value)
+{
+	return ERR_PTR(-ENODEV);
+}
+
 static inline struct dentry *debugfs_create_bool(const char *name, mode_t mode,
 						 struct dentry *parent,
 						 u32 *value)