[RISCV] Regenerate test/CodeGen/RISCV/legalize-fneg.ll after rL356068

rL356068 caused some minor re-orderings. Regenerate legalize-fneg.ll to
reflect this, and remove the NOLIB check lines (they're redundant given that
the RV32I and RV64I check lines generated by update_llc_test_checks.py already
demonstrate there is no libcall).

llvm-svn: 356074