When page size is 64K, RX buffer is currently not reused when the
page_offset is moved to last buffer. This patch adds checking to
decide whether the buffer page can be reused when last_offset is
moved beyond last offset.

If the driver is the only user of page when page_offset is moved
to beyond last offset, then buffer can be reused and page_offset
is set to zero.
Signed-off-by: NYunsheng Lin <linyunsheng@huawei.com>
Signed-off-by: NHuazhong Tan <tanhuazhong@huawei.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>