Extend nops num in "maybe_gen_insn" for RISC-V Vector intrinsics

Hi, current maybe_gen_insn can only expand 9 nops.
For RVV intrinsics, I need to extend it as 10, otherwise I should use GEN_FCN.
This patch is quite obvious change, Ok for trunk ?

Thanks.

gcc/ChangeLog:

	* config/riscv/riscv-vector-builtins.cc
	(function_expander::use_ternop_insn): Use maybe_gen_insn instead.
	(function_expander::use_widen_ternop_insn): Ditto.
	* optabs.cc (maybe_gen_insn): Extend nops handling.