ipvs: change type of netns_ipvs->sysctl_sync_qlen_max

This member of struct netns_ipvs is calculated from nr_free_buffer_pages
so change its type to unsigned long in case of overflow.  Also, type of
its related proc var sync_qlen_max and the return type of function
sysctl_sync_qlen_max() should be changed to unsigned long, too.

Besides, the type of ipvs_master_sync_state->sync_queue_len should be
changed to unsigned long accordingly.

Signed-off-by: Zhang Yanfei <zhangyanfei@cn.fujitsu.com>
Cc: Julian Anastasov <ja@ssi.bg>
Cc: David Miller <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Simon Horman <horms@verge.net.au>