RISC-V: Bugfix vfmv insn honor zvfhmin for FP16 SEW [PR115763]

According to the ISA,  the zvfhmin sub extension should only contain
convertion insn.  Thus,  the vfmv insn acts on FP16 should not be
present when only the zvfhmin option is given.

This patch would like to fix it by split the pred_broadcast define_insn
into zvfhmin and zvfh part.  Given below example:

void test (_Float16 *dest, _Float16 bias) {
  dest[0] = bias;
  dest[1] = bias;
}

when compile with -march=rv64gcv_zfh_zvfhmin

Before this patch:
test:
  vsetivli        zero,2,e16,mf4,ta,ma
  vfmv.v.f        v1,fa0 // should not leverage vfmv for zvfhmin
  vse16.v v1,0(a0)
  ret

After this patch:
test:
  addi     sp,sp,-16
  fsh      fa0,14(sp)
  addi     a5,sp,14
  vsetivli zero,2,e16,mf4,ta,ma
  vlse16.v v1,0(a5),zero
  vse16.v  v1,0(a0)
  addi     sp,sp,16
  jr       ra

	PR target/115763

gcc/ChangeLog:

	* config/riscv/vector.md (*pred_broadcast<mode>): Split into
	zvfh and zvfhmin part.
	(*pred_broadcast<mode>_zvfh): New define_insn for zvfh part.
	(*pred_broadcast<mode>_zvfhmin): Ditto but for zvfhmin.

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/rvv/base/scalar_move-5.c: Adjust asm check.
	* gcc.target/riscv/rvv/base/scalar_move-6.c: Ditto.
	* gcc.target/riscv/rvv/base/scalar_move-7.c: Ditto.
	* gcc.target/riscv/rvv/base/scalar_move-8.c: Ditto.
	* gcc.target/riscv/rvv/base/pr115763-1.c: New test.
	* gcc.target/riscv/rvv/base/pr115763-2.c: New test.

Signed-off-by: Pan Li <pan2.li@intel.com>