kmap: remove kmap_atomic_to_page()

kmap_atomic_to_page() has no callers and is only defined on 1 arch and
declared on another.  Remove it.
Suggested-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Christian König <christian.koenig@amd.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Chris Zankel <chris@zankel.net>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Helge Deller <deller@gmx.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/20200507150004.1423069-13-ira.weiny@intel.comSigned-off-by: Linus Torvalds <torvalds@linux-foundation.org>

arch/csky/include/asm/highmem.h

@@ -33,7 +33,6 @@ extern pte_t *pkmap_page_table;
 #define ARCH_HAS_KMAP_FLUSH_TLB
 extern void kmap_flush_tlb(unsigned long addr);
 extern void *kmap_atomic_pfn(unsigned long pfn);
-extern struct page *kmap_atomic_to_page(void *ptr);
 
 #define flush_cache_kmaps() do {} while (0)
 

arch/csky/mm/highmem.c

@@ -81,19 +81,6 @@ void *kmap_atomic_pfn(unsigned long pfn)
 	return (void *) vaddr;
 }
 
-struct page *kmap_atomic_to_page(void *ptr)
-{
-	unsigned long idx, vaddr = (unsigned long)ptr;
-	pte_t *pte;
-
-	if (vaddr < FIXADDR_START)
-		return virt_to_page(ptr);
-
-	idx = virt_to_fix(vaddr);
-	pte = kmap_pte - (idx - FIX_KMAP_BEGIN);
-	return pte_page(*pte);
-}
-
 static void __init kmap_pages_init(void)
 {
 	unsigned long vaddr;

arch/nds32/include/asm/highmem.h

@@ -52,7 +52,6 @@ extern void kmap_init(void);
  */
 #ifdef CONFIG_HIGHMEM
 extern void *kmap_atomic_pfn(unsigned long pfn);
-extern struct page *kmap_atomic_to_page(void *ptr);
 #endif
 
 #endif