[llvm] [RISCV] Check SP-relative offset in needsFrameBaseReg when FP offset overflows (PR #197368)

[Garvit Gupta via llvm-commits]

quic-garvgupt wrote:

| Metric | Value |
|---|---|
| FP overhead (unpatched) | +5.14% vs -fomit-fp |
| FP overhead (patched) | +2.66% vs -fomit-fp |
| Patch savings | -2.36% vs unpatched -fno-omit-fp |
| Patch recovers | 48.2% of the frame pointer overhead |

The above numbers represent the net savings from this PR combined with https://github.com/llvm/llvm-project/pull/193962.

https://github.com/llvm/llvm-project/pull/197368