[S390] Remove unncessary export of arch_pick_mmap_layout

This function is defined for use in exec, not in modules.
No other architecture exports its implementation.

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/mm/mmap.c b/arch/s390/mm/mmap.c
index a0155c0..2857c48 100644
--- a/arch/s390/mm/mmap.c
+++ b/arch/s390/mm/mmap.c
@@ -100,7 +100,6 @@
 		mm->unmap_area = arch_unmap_area_topdown;
 	}
 }
-EXPORT_SYMBOL_GPL(arch_pick_mmap_layout);
 
 #else
 
@@ -175,6 +174,5 @@
 		mm->unmap_area = arch_unmap_area_topdown;
 	}
 }
-EXPORT_SYMBOL_GPL(arch_pick_mmap_layout);
 
 #endif