Fix unaligned load in AC-TILE MPM.

The SLOAD define using __insn_ld2s_L2 is used to provide a compiler
hint that the load will come from the L2 cache instead of the L1. It
also specifies that it is a 2 byte signed load. For the Tiny MPM, that
needs to be a 1-byte load, which is what is specified in util-ac-mpm-tile.c,
but the #undef was removing that definition

This fixes unalgned loads,but it could also fix a real bug.

Passed  prscript.
https://buildbot.suricata-ids.org/builders/ken-tilera-pcap/builds/69
https://buildbot.suricata-ids.org/builders/ken-tilera/builds/135