maple: change the pointer name from maple_enode to maple_enode_p

The current name of the pointer to struct maple_enode is also
maple_enode. This is correct from the grammar point but can be
comfusing. Besides it seems in Linux it prefers typedef struct foo
*foo_p;, e.g. typedef struct cpumask *cpumask_var_t; and typedef
struct cgraph_node *cgraph_node_ptr;. I use re to search in the
Linux project and cannot find another example in typedef struct
foo *foo; style.

This also results in a bug in the bindings of the
rust-for-linux subsystem, which can be seen in this github issue.

Rust-for-Linux#795

The struct pointer maple_enode and maple_pnode are not used. It is
safe to change it to a new name.

Signed-off-by: Li Hongyu <[email protected]>

Author: Richardhongyu

include/linux/maple_tree.h

@@ -72,8 +72,8 @@
  *   0x010 : 32 bit values, type in 0-2, slot in 3-6
  *   0x110 : 64 bit values, type in 0-2, slot in 3-6
  */
-typedef struct maple_enode *maple_enode; /* encoded node */
-typedef struct maple_pnode *maple_pnode; /* parent node */
+typedef struct maple_enode *maple_enode_p; /* encoded node */
+typedef struct maple_pnode *maple_pnode_p; /* parent node */
 
 /*
  * This metadata is used to optimize the gap updating code and in reverse