Fix MIPS builds with current trunk

[Matthew Fortune]

Jeff Law <law@redhat.com> writes:
> All the MIPS compilers will fail to build using the trunk due to a
> couple minor uninitialized memory issues.
> 
> First in mips_multi_add we add an uninitialized mips_multi_member object
> to the mips_multi_members vec.  It's easy enough to just memset the new
> member.
> 
> Second in mips_expand_vec_perm_const the tail of the orig_perm may be
> uninitialized if the number of elements in the target object is smaller
> than MAX_VECT_LEN.  This is also trivial to fix by explicitly clearing
> the tail of the array.
> 
> Tested by verifying the MIPS targets in config-list.mk will build using
> a trunk compiler again.
> 
> Installed on the trunk.

Thanks Jeff, and apologies for missing the report.

Matthew