fs/proc/internal.h: shuffle "struct pde_opener"

List iteration takes more code than anything else which means embedded
list_head should be the first element of the structure.

Space savings:

	add/remove: 0/0 grow/shrink: 0/4 up/down: 0/-18 (-18)
	Function                                     old     new   delta
	close_pdeo                                   228     227      -1
	proc_reg_release                              86      82      -4
	proc_entry_rundown                           143     139      -4
	proc_reg_open                                298     289      -9

Link: http://lkml.kernel.org/r/20191004234753.GB30246@avx2
Signed-off-by: Alexey Dobriyan <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

fs/proc/internal.h

@@ -197,8 +197,8 @@ extern ssize_t proc_simple_write(struct file *, const char __user *, size_t, lof
  * inode.c
  */
 struct pde_opener {
-	struct file *file;
 	struct list_head lh;
+	struct file *file;
 	bool closing;
 	struct completion *c;
 } __randomize_layout;