[mips] When double precision loads and stores are split into two i32 loads and

[mips] When double precision loads and stores are split into two i32 loads and
stores, make sure the load or store that accesses the higher half does not have
an alignment that is larger than the offset from the original address.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@190318 91177308-0d34-0410-b5e6-96231b3b80d8