net: ipv6: Optimize ipv6 packet matching

iptables matching for ipv6 always has a mask if an address is
specified for match. Adding a check for mask prior to that
helps to improve performance as it avoids the masked comparison.
This is achieved by defining a new feature IP6_NF_IPTABLES_128
which allows to perform 128 bit arithmetic while matching.

CRs-Fixed: 2122802
Change-Id: I9ffd34e29d1b06ad74545d4751aa0e1ea06ded49
Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>