Limit the maximal range of consecutive elements to add/delete

Limit the maximal range of consecutive elements to add/delete

The range size of consecutive elements were not limited. Thus one
could define a huge range which may result soft lockup errors due
to the long execution time. Now the range size is limited to 2^20
entries. Reported by Brad Spengler.

Signed-off-by: Jozsef Kadlecsik <kadlec@netfilter.org>