RISC-V: Adjust expand_cond_len_{unary,binop,op} api

RISC-V: Adjust expand_cond_len_{unary,binop,op} api

This patch change expand_cond_len_{unary,binop}'s argument `rtx_code code`
to `unsigned icode` and use the icode directly to determine whether the
rounding_mode operand is required.

gcc/ChangeLog:

	* config/riscv/autovec.md: Adjust.
	* config/riscv/riscv-protos.h (expand_cond_len_unop): Ditto.
	(expand_cond_len_binop): Ditto.
	* config/riscv/riscv-v.cc (needs_fp_rounding): Ditto.
	(expand_cond_len_op): Ditto.
	(expand_cond_len_unop): Ditto.
	(expand_cond_len_binop): Ditto.
	(expand_cond_len_ternop): Ditto.