RISC-V: Handle out-of-range calls to undefined weak.

	bfd/
	PR ld/23244
	* elfnn-riscv.c (riscv_elf_relocate_section) <R_RISCV_CALL>: Check
	for and handle an undefined weak with no PLT.

	ld/
	* testsuite/ld-riscv-elf/ld-riscv-elf.exp: Run new weak ref tests.
	* testsuite/ld-riscv-elf/weakref.ld: New.
	* testsuite/ld-riscv-elf/weakref32.d: New.
	* testsuite/ld-riscv-elf/weakref32.s: New.
	* testsuite/ld-riscv-elf/weakref64.d: New.
	* testsuite/ld-riscv-elf/weakref64.s: New.