mm/mempolicy: Remove CONFIG_TMPFS from mpol_parse_str in headers

Commit 24993d7 ("mm/numa: Allow override of kernel's default NUMA policy")
removed the #ifdef CONFIG_TMPFS guard from the function definition
for mpol_parse_str, but not for the prototype. This lead to build errors/
warnings should CONFIG_TMPFS be disabled.

Fixes: 24993d7 ("mm/numa: Allow override of kernel's default NUMA policy")
Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>

Author: 6by9

include/linux/mempolicy.h

@@ -160,10 +160,7 @@ static inline void check_highest_zone(enum zone_type k)
 int do_migrate_pages(struct mm_struct *mm, const nodemask_t *from,
 		     const nodemask_t *to, int flags);
 
-
-#ifdef CONFIG_TMPFS
 extern int mpol_parse_str(char *str, struct mempolicy **mpol);
-#endif
 
 extern void mpol_to_str(char *buffer, int maxlen, struct mempolicy *pol);