[RISCV] Add tests for F/D with non-FP ABI to interrupt-attr.ll. NFC

Without a floating point aware ABI for callees, an interrupt handler
needs to save all floating point registers even normally callee saved.

We are currently unnecessarily saving callee saved FP registers when
a floating point ABI is used by the callee. This is different than gcc
as noted in this discourse
post https://discourse.llvm.org/t/has-bugs-when-optimizing-save-restore-csrs-by-changing-csr-xlen-f32-interrupt/78200/1

Author: topperc