RISC-V: testsuite: Fix vmul test expectation and fix -ffast-math.

RISC-V: testsuite: Fix vmul test expectation and fix -ffast-math.

I forgot to check for vfmul in the multiplication tests as well as
some -ffast-math arguments.  Fix this.

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/rvv/autovec/binop/vadd-run.c: Add
	-ffast-math.
	* gcc.target/riscv/rvv/autovec/binop/vadd-zvfh-run.c: Dito.
	* gcc.target/riscv/rvv/autovec/binop/vrem-rv32gcv.c: Remove
	-ffast-math
	* gcc.target/riscv/rvv/autovec/binop/vmul-rv32gcv.c: Check for
	vfmul.
	* gcc.target/riscv/rvv/autovec/binop/vmul-rv64gcv.c: Dito.