Revert "[llvm][RISCV] Enable trailing fences for seq-cst stores by default (#87376)"

This reverts commit 733b271d.

Reverting in order to revert the companion patch adding the atomics ABI
ELF attributes due to the reported incompatibility with GNU ld.
https://github.com/llvm/llvm-project/pull/84597#issuecomment-2079128332