l4p/tcp: fix SIGSEGV when reading IPv6 address

l4p/tcp: fix SIGSEGV when reading IPv6 address

IPv6 address is obtained through pointer to mbuf (part storing IPv6
addr). Structure which then holds that pointer defines it as a pointer
to _m128i data type. Because of that, when code is optimized,
instruction vmovdqa is used, which requires data to be aligned to
16-bytes. Pointer from mbuf does not have to be aligned in that way,
which may cause SIGSEGV.

Solution is to add attribute packed and aligned(1) to structure holding
IPv6 address. With that, vmovdqu assembly instruction is used, which is
the equivalent of vmovdqa, but for unaligned data.

Signed-off-by: Mariusz Drost <mariuszx.drost@intel.com>
Change-Id: I66e7ce2a317de2cdbc763ec8e31141605b5e5469