[libc][riscv] Added support for rv32 in setjmp and longjmp

This patch adds two new macros to setjmp (STORE, STORE_FP) and two new
macros to longjmp (LOAD, LOAD_FP) that takes a register and a buff, then
select the correct asm instruction for rv32 and rv64.

Reviewed By: sivachandra

Differential Revision: https://reviews.llvm.org/D158640