mips: add different value for SOCK_STREAM

MIPS uses different values for socket types.
This is protected by ARCH_HAS_SOCKET_TYPES in Linux kernel and we introduce
it here too. This is important for log-socket feature, and it resolves the
issue reported in https://bugs.kde.org/show_bug.cgi?id=313267#c21.


git-svn-id: svn://svn.valgrind.org/valgrind/trunk@13359 a5019735-40e9-0310-863c-91ae7b9d1cf9