[mips][msa] Combine binsri-like DAG of AND and OR into equivalent VSELECT

[mips][msa] Combine binsri-like DAG of AND and OR into equivalent VSELECT

(or (and $a, $mask), (and $b, $inverse_mask)) => (vselect $mask, $a, $b).
where $mask is a constant splat. This allows bitwise operations to make use
of bsel.

It's also a stepping stone towards matching bins[lr], and bins[lr]i from
normal IR.

Two sets of similar tests have been added in this commit. The bsel_* functions
test the case where binsri cannot be used. The binsr_*_i functions will
start to use the binsri instruction in the next commit.

llvm-svn: 193682