powerpc/mm: Remove flush_tlb_page_nohash() prototype.

flush_tlb_page_nohash() was removed by
commit 703b41ad ("powerpc/mm: remove flush_tlb_page_nohash")

Remove stale prototype and comment.
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/4a58831da6d6ba4fe309b94aa1dd8f02982d46b2.1603348103.git.christophe.leroy@csgroup.eu

arch/powerpc/include/asm/book3s/32/tlbflush.h

@@ -8,7 +8,6 @@
  */
 extern void flush_tlb_mm(struct mm_struct *mm);
 extern void flush_tlb_page(struct vm_area_struct *vma, unsigned long vmaddr);
-extern void flush_tlb_page_nohash(struct vm_area_struct *vma, unsigned long addr);
 extern void flush_tlb_range(struct vm_area_struct *vma, unsigned long start,
 			    unsigned long end);
 extern void flush_tlb_kernel_range(unsigned long start, unsigned long end);

arch/powerpc/include/asm/nohash/tlbflush.h

@@ -10,7 +10,6 @@
  *  - local_flush_tlb_mm(mm, full) flushes the specified mm context on
  *                           the local processor
  *  - local_flush_tlb_page(vma, vmaddr) flushes one page on the local processor
- *  - flush_tlb_page_nohash(vma, vmaddr) flushes one page if SW loaded TLB
  *  - flush_tlb_range(vma, start, end) flushes a range of pages
  *  - flush_tlb_kernel_range(start, end) flushes a range of kernel pages
  *