powerpc/mm: Silence unused-but-set-variable warnings

pte_unmap() compiles away on some powerpc platforms, so silence the
warnings below by making it a static inline function.

  mm/memory.c: In function 'copy_pte_range':
  mm/memory.c:820:24: warning: variable 'orig_dst_pte' set but not used
  mm/memory.c:820:9: warning: variable 'orig_src_pte' set but not used
  mm/madvise.c: In function 'madvise_free_pte_range':
  mm/madvise.c:318:9: warning: variable 'orig_pte' set but not used
  mm/swap_state.c: In function 'swap_ra_info':
  mm/swap_state.c:634:15: warning: variable 'orig_pte' set but not used
Suggested-by: NChristophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: NQian Cai <cai@lca.pw>
Reviewed-by: NChristophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>

arch/powerpc/include/asm/book3s/64/pgtable.h

@@ -992,7 +992,8 @@ extern struct page *pgd_page(pgd_t pgd);
 	(((pte_t *) pmd_page_vaddr(*(dir))) + pte_index(addr))
 
 #define pte_offset_map(dir,addr)	pte_offset_kernel((dir), (addr))
-#define pte_unmap(pte)			do { } while(0)
+
+static inline void pte_unmap(pte_t *pte) { }
 
 /* to find an entry in a kernel page-table-directory */
 /* This now only contains the vmalloc pages */

arch/powerpc/include/asm/nohash/64/pgtable.h

@@ -205,7 +205,8 @@ static inline void pgd_set(pgd_t *pgdp, unsigned long val)
   (((pte_t *) pmd_page_vaddr(*(dir))) + (((addr) >> PAGE_SHIFT) & (PTRS_PER_PTE - 1)))
 
 #define pte_offset_map(dir,addr)	pte_offset_kernel((dir), (addr))
-#define pte_unmap(pte)			do { } while(0)
+
+static inline void pte_unmap(pte_t *pte) { }
 
 /* to find an entry in a kernel page-table-directory */
 /* This now only contains the vmalloc pages */