[PATCH] Update pfn_cyclic when the cyclic buffer size is corrected.

When the clearing bit operation for excluding free pages can overrun
the cyclic buffer, the buffer size is changed with
check_cyclic_buffer_overrun().
Then pfn_cyclic should be recalculated.

Reviewed-by: HATAYAMA Daisuke <d.hatayama@jp.fujitsu.com>
Signed-off-by: Atsushi Kumagai <kumagai-atsushi@mxc.nes.nec.co.jp>