RISC-V: Export some functions from riscv-vsetvl to riscv-v[NFC]

RISC-V: Export some functions from riscv-vsetvl to riscv-v[NFC]

Address kito's comments of AVL propagation patch.

Export the functions that are not only used by VSETVL PASS but also AVL propagation PASS.

No functionality change.
gcc/ChangeLog:

	* config/riscv/riscv-protos.h (has_vl_op): Export from riscv-vsetvl to riscv-v
	(tail_agnostic_p): Ditto.
	(validate_change_or_fail): Ditto.
	(nonvlmax_avl_type_p): Ditto.
	(vlmax_avl_p): Ditto.
	(get_sew): Ditto.
	(enum vlmul_type): Ditto.
	(count_regno_occurrences): Ditto.
	* config/riscv/riscv-v.cc (has_vl_op): Ditto.
	(get_default_ta): Ditto.
	(tail_agnostic_p): Ditto.
	(validate_change_or_fail): Ditto.
	(nonvlmax_avl_type_p): Ditto.
	(vlmax_avl_p): Ditto.
	(get_sew): Ditto.
	(enum vlmul_type): Ditto.
	(get_vlmul): Ditto.
	(count_regno_occurrences): Ditto.
	* config/riscv/riscv-vsetvl.cc (vlmax_avl_p): Ditto.
	(has_vl_op): Ditto.
	(get_sew): Ditto.
	(get_vlmul): Ditto.
	(get_default_ta): Ditto.
	(tail_agnostic_p): Ditto.
	(count_regno_occurrences): Ditto.
	(validate_change_or_fail): Ditto.