[Clang][LoongArch] Add inline asm support for constraints k/m/ZB/ZC

k: A memory operand whose address is formed by a base register and
(optionally scaled) index register.

m: A memory operand whose address is formed by a base register and
offset that is suitable for use in instructions with the same
addressing mode as st.w and ld.w.

ZB: An address that is held in a general-purpose register. The offset
is zero.

ZC: A memory operand whose address is formed by a base register and
offset that is suitable for use in instructions with the same
addressing mode as ll.w and sc.w.

Differential Revision: https://reviews.llvm.org/D134638