RISC-V: Use safe_grow_cleared for vector info [PR111649]

RISC-V: Use safe_grow_cleared for vector info [PR111649]

Resolves a riscv*-*-* bootstrap failure due to a newly-turned-on assert.

2023-09-30  Jakub Jelinek  <jakub@redhat.com>

gcc/ChangeLog:

	PR target/111649

	* config/riscv/riscv-vsetvl.cc (vector_infos_manager::vector_infos_manager):
	Replace safe_grow with safe_grow_cleared.