RISC-V: Fixed overwritten IRELATIVE relocs in the .rel.iplt for data reloc.

RISC-V: Fixed overwritten IRELATIVE relocs in the .rel.iplt for data reloc.

This was originally reported by Hau Hsu <hau.hsu@sifive.com>.

Similar to commit 51a8a7c2e3cc0730831963651a55d23d1fae624d

We shouldn't use riscv_elf_append_rela to add dynamic relocs into .rela.iplt
in the riscv_elf_relocate_section when handling ifunc data reloc R_RISCV_32/64.
This just like what did in the riscv_elf_finish_dynamic_symbol.

bfd/
	* elfnn-riscv.c (riscv_elf_relocate_section): We shouldn't use
	riscv_elf_append_rela to add dynamic relocs into .rela.iplt in the
	riscv_elf_relocate_section when handling ifunc data reloc.
ld/
	* testsuite/ld-riscv-elf/ifunc-overwrite.s: Updated and renamed.
	* testsuite/ld-riscv-elf/ifunc-overwrite-exe.rd: Likewise.
	* testsuite/ld-riscv-elf/ifunc-overwrite-pic.rd: Likewise.
	* testsuite/ld-riscv-elf/ifunc-overwrite-pie.rd: Likewise.
	* testsuite/ld-riscv-elf/ifunc-overwrite.d: Renamed.