RISC-V: Fix non-obvious comment typos

RISC-V: Fix non-obvious comment typos

This fixes the remainder of the typos I found when reading various parts of the
RISC-V backend.

gcc/ChangeLog:

	* config/riscv/riscv-v.cc (legitimize_move): extrac -> extract.
	(expand_vec_cmp_float): Remove duplicate vmnor.mm.
	* config/riscv/riscv-vector-builtins.cc: ins -> insns.
	* config/riscv/riscv.cc (riscv_init_machine_status): mwrvv -> mrvv.
	* config/riscv/vector-iterators.md: RVVM8QImde -> RVVM8QImode
	* config/riscv/vector.md: Replaced non-existant vsetivl with vsetivli.

Signed-off-by: Patrick O'Neill <patrick@rivosinc.com>