[llvm] [RISCV] fix SP recovery in a function epilogue (PR #110809)

[via llvm-commits]

eaeltsin wrote:

I'm not sure about crashing, but looking at disassembler at https://godbolt.org/z/z8Kehr5ob:

The new code for function foo has prologue
```
        addi    sp, sp, -496
        sd      ra, 424(sp)
        sd      s0, 416(sp)
        addi    s0, sp, 432
```
and epilogue
```
        addi    sp, s0, -496  <---- should be 432
        ld      ra, 424(sp)
        ld      s0, 416(sp)
        addi    sp, sp, 496
        ret
```

https://github.com/llvm/llvm-project/pull/110809