highmem: Export totalhigh_pages.

Hash et al. sizing code in SCTP wants to make the
calculation totalram_pages - totalhigh_pages, just
like TCP.  But this requires an export for the
CONFIG_HIGHMEM case to work.
Signed-off-by: David S. Miller <davem@davemloft.net>

mm/highmem.c

@@ -40,6 +40,7 @@
 #ifdef CONFIG_HIGHMEM
 
 unsigned long totalhigh_pages __read_mostly;
+EXPORT_SYMBOL(totalhigh_pages);
 
 unsigned int nr_free_highpages (void)
 {