RISC-V: Fix typos in code or comment [NFC]

RISC-V: Fix typos in code or comment [NFC]

Just found some typo when fixing bugs and then use aspell to find few
more typos, this patch didn't do anything other than fix typo.

gcc/ChangeLog:

	* config/riscv/riscv-vsetvl.cc: Fix typos in comments.
	(get_all_predecessors): Ditto.
	(pre_vsetvl::m_unknow_info): Rename to...
	(pre_vsetvl::m_unknown_info): this.
	(pre_vsetvl::compute_vsetvl_def_data): Rename m_unknow_info to
	m_unknown_info.
	(pre_vsetvl::cleaup): Rename to...
	(pre_vsetvl::cleanup): this.
	(pre_vsetvl::compute_vsetvl_def_data): Fix typos.
	(pass_vsetvl::lazy_vsetvl): Update function name and fix typos.
	* config/riscv/riscv.cc: Fix typos in comments.
	(struct machine_function): Fix typo in comments.
	(riscv_valid_lo_sum_p): Ditto.
	(riscv_force_address): Ditto.
	(riscv_immediate_operand_p): Ditto.
	(riscv_in_small_data_p): Ditto.
	(riscv_first_stack_step): Ditto.
	(riscv_expand_prologue): Ditto.
	(riscv_convert_vector_chunks): Ditto.
	(riscv_override_options_internal): Ditto.
	(get_common_costs): Ditto.