RISC-V: Remove tail && mask policy operand for vmclr, vmset, vmld, vmst

RISC-V: Remove tail && mask policy operand for vmclr, vmset, vmld, vmst

1. vector.md: remove tail && mask policy operand for mask mode operations since
   we don't need them according to RVV ISA.
2. riscv-v.cc: adapt emit_pred_op for mask mode predicated mov since all RVV modes
   including vector integer mode && vector float mode  && vector bool mode are
   all use emit_pred_op function. For vector integer mode && vector float mode,
   we have instruction like vle.v/vse.v that we need tail && mask policy.
   However, for vector bool mode, the instruction is vlm/vsm that we don't need
   tail && mask policy. So we add a condition here to add tail && mask policy operand
   during expand if it is not a vector bool modes.

This patch is to cleanup the code and make it be consistent with RVV ISA.

gcc/ChangeLog:

	* config/riscv/riscv-v.cc (emit_pred_op): Adapt for mask mode.
	* config/riscv/vector.md: Remove Tail && make policy operand for mask mode mov.