mm-correctly-update-zone-managed_pages-fix-fix

mm-correctly-update-zone-managed_pages-fix-fix

When CONFIG_HIGHMEM is undefined, totalhigh_pages is defined as:
#define totalhigh_pages 0UL
Thus statement "totalhigh_pages += count" will cause build failure as:
  CC      mm/page_alloc.o
mm/page_alloc.c: In function `adjust_managed_page_count':
mm/page_alloc.c:5262:19: error: lvalue required as left operand of
assignment
make[1]: *** [mm/page_alloc.o] Error 1
make: *** [mm/page_alloc.o] Error 2

So we still need to use CONFIG_HIGHMEM to guard the statement.

Cc: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>