RISC-V: Rename some variables of vector_block_info[NFC]

1. Remove "m_" prefix as they are not private members.
2. Rename infos -> local_infos, info -> global_info to clarify their meaning.

Pushed as it is obvious.

gcc/ChangeLog:

	* config/riscv/riscv-vsetvl.cc (pre_vsetvl::fuse_local_vsetvl_info): Rename variables.
	(pre_vsetvl::pre_global_vsetvl_info): Ditto.
	(pre_vsetvl::emit_vsetvl): Ditto.