[LoongArch] Add codegen support for the binary operations

These binary operations include sub/fadd/fsub/fmul/fdiv. Others ops
like mul/udiv/sdiv/urem/srem would be added later since they depend on
`shift` and `truncate` that have not been supported.

Note `add` has been added in a previous patch.

Reference:
https://llvm.org/docs/LangRef.html#binary-operations

Differential Revision: https://reviews.llvm.org/D127199