arm64: mm: remove unnecessary EXPORT_SYMBOL_GPL

arch_pick_mmap_layout is only called by fs/exec.c which is always built into
kernel, it looks the EXPORT_SYMBOL_GPL is pointless and no architectures export
it other than ARM64.
Signed-off-by: Yang Shi <yang.shi@linaro.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>

arch/arm64/mm/mmap.c

@@ -95,8 +95,6 @@ void arch_pick_mmap_layout(struct mm_struct *mm)
 		mm->get_unmapped_area = arch_get_unmapped_area_topdown;
 	}
 }
-EXPORT_SYMBOL_GPL(arch_pick_mmap_layout);
-
 
 /*
  * You really shouldn't be using read() or write() on /dev/mem.  This might go