powerpc/hugetlbfs: Export HPAGE_SHIFT

Export it so it can be referenced inside a module.
Signed-off-by: Oliver O'Halloran <oohall@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/mm/hugetlbpage.c

@@ -32,6 +32,7 @@
 #define PAGE_SHIFT_16G	34
 
 unsigned int HPAGE_SHIFT;
+EXPORT_SYMBOL(HPAGE_SHIFT);
 
 /*
  * Tracks gpages after the device tree is scanned and before the