RISC-V: Fix more splitters accidentally calling gen_reg_rtx.

RISC-V: Fix more splitters accidentally calling gen_reg_rtx.

	PR target/91683
	* config/riscv/riscv-protos.h (riscv_split_symbol): New bool parameter.
	(riscv_move_integer): Likewise.
	* config/riscv/riscv.c (riscv_split_integer): Pass FALSE for new
	riscv_move_integer arg.
	(riscv_legitimize_move): Likewise.
	(riscv_force_temporary): New parameter in_splitter.  Don't call
	force_reg if true.
	(riscv_unspec_offset_high): Pass FALSE for new riscv_force_temporary
	arg.
	(riscv_add_offset): Likewise.
	(riscv_split_symbol): New parameter in_splitter.  Pass to
	riscv_force_temporary.
	(riscv_legitimize_address): Pass FALSE for new riscv_split_symbol
	arg.
	(riscv_move_integer): New parameter in_splitter.  New local
	can_create_psuedo.  Don't call riscv_split_integer or force_reg when
	in_splitter TRUE.
	(riscv_legitimize_const_move): Pass FALSE for new riscv_move_integer,
	riscv_split_symbol, and riscv_force_temporary args.
	* config/riscv/riscv.md (low<mode>+1): Pass TRUE for new
	riscv_move_integer arg.
	(low<mode>+2): Pass TRUE for new riscv_split_symbol arg.

From-SVN: r275925