ia64: contig/paging_init: reduce code duplication

The FLATMEM version of paging_init has calls to free_area_init_nodes() in
the end of every branch of 'if' and 'ifdef' statements.

Let's call this function outside the 'ifdef' and 'if' statements instead.

Signed-off-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>