RISC-V: Add pattern for vector-scalar floating-point max

RISC-V: Add pattern for vector-scalar floating-point max

This pattern enables the combine pass (or late-combine, depending on the case)
to merge a vec_duplicate into an smax RTL instruction.

Before this patch, we have two instructions, e.g.:
  vfmv.v.f       v2,fa0
  vfmax.vv       v1,v1,v2

After, we get only one:
  vfmax.vf       v1,v1,fa0

In some cases, it also shaves off one vsetvli.

gcc/ChangeLog:

	* config/riscv/autovec-opt.md (*vfmax_vf_<mode>): Rename into...
	(*vf<optab>_vf_<mode>): New pattern to combine vec_duplicate +
	vf{min,max}.vv into vf{max,min}.vf.

gcc/testsuite/ChangeLog:
	* gcc.target/riscv/rvv/autovec/vls/floating-point-max-2.c: Adjust scan
	dump.
	* gcc.target/riscv/rvv/autovec/vls/floating-point-max-4.c: Likewise.
	* gcc.target/riscv/rvv/autovec/vx_vf/vf-1-f16.c: Add vfmax. Also add
	missing scan-dump for vfmul.
	* gcc.target/riscv/rvv/autovec/vx_vf/vf-1-f32.c: Add vfmax.
	* gcc.target/riscv/rvv/autovec/vx_vf/vf-1-f64.c: Likewise.
	* gcc.target/riscv/rvv/autovec/vx_vf/vf-2-f16.c: Likewise.
	* gcc.target/riscv/rvv/autovec/vx_vf/vf-2-f32.c: Likewise.
	* gcc.target/riscv/rvv/autovec/vx_vf/vf-2-f64.c: Likewise.
	* gcc.target/riscv/rvv/autovec/vx_vf/vf-3-f16.c: Likewise.
	* gcc.target/riscv/rvv/autovec/vx_vf/vf-3-f32.c: Likewise.
	* gcc.target/riscv/rvv/autovec/vx_vf/vf-3-f64.c: Likewise.
	* gcc.target/riscv/rvv/autovec/vx_vf/vf-4-f16.c: Likewise.
	* gcc.target/riscv/rvv/autovec/vx_vf/vf-4-f32.c: Likewise.
	* gcc.target/riscv/rvv/autovec/vx_vf/vf-4-f64.c: Likewise.
	* gcc.target/riscv/rvv/autovec/vx_vf/vf_binop.h: Add max functions.
	* gcc.target/riscv/rvv/autovec/vx_vf/vf_binop_data.h: Add data for
	vfmax.
	* gcc.target/riscv/rvv/autovec/vx_vf/vf_vfmax-run-1-f16.c: New test.
	* gcc.target/riscv/rvv/autovec/vx_vf/vf_vfmax-run-1-f32.c: New test.
	* gcc.target/riscv/rvv/autovec/vx_vf/vf_vfmax-run-1-f64.c: New test.