bfd: riscv_maybe_function_sym check _bfd_elf_is_local_label_name

This fixes the ld "Handle no DWARF information" testcase. Which
currently fails on riscv because a local label name is assumed
to be the current function name.

bfd/ChangeLog:

* elfnn-riscv.c (riscv_maybe_function_sym): Also check
	_bfd_elf_is_local_label_name.