mm: nommu: kill arch_get_unmapped_area()

When nommu, the arch_get_unmapped_area() will not be called, just kill
it.

Link: https://lkml.kernel.org/r/20210910061906.36299-1-wangkefeng.wang@huawei.com
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

mm/nommu.c

@@ -1639,12 +1639,6 @@ int remap_vmalloc_range(struct vm_area_struct *vma, void *addr,
 }
 EXPORT_SYMBOL(remap_vmalloc_range);
 
-unsigned long arch_get_unmapped_area(struct file *file, unsigned long addr,
-	unsigned long len, unsigned long pgoff, unsigned long flags)
-{
-	return -ENOMEM;
-}
-
 vm_fault_t filemap_fault(struct vm_fault *vmf)
 {
 	BUG();