RISC-V: Use pc-relative relocation for FDE initial location
The symbol address in .eh_frame may be adjusted in
_bfd_elf_discard_section_eh_frame, and the content of .eh_frame will be
adjusted in _bfd_elf_write_section_eh_frame. Therefore, we cannot insert
a relocation whose addend symbol is in .eh_frame. Othrewise, the value
may be adjusted twice.