kernel/memremap.c: remove the unused device_private_entry_fault() export

This export has been entirely unused since it was added more than 1 1/2
years ago.

Link: http://lkml.kernel.org/r/20190429115535.12793-1-hch@lst.deSigned-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/memremap.c

@@ -45,7 +45,6 @@ vm_fault_t device_private_entry_fault(struct vm_area_struct *vma,
 	 */
 	return devmem->page_fault(vma, addr, page, flags, pmdp);
 }
-EXPORT_SYMBOL(device_private_entry_fault);
 #endif /* CONFIG_DEVICE_PRIVATE */
 
 static void pgmap_array_delete(struct resource *res)