RISC-V: Protect .got with relro

Move .got before .data so that it can be protected with -zrelro.  Also
separate .got.plt from .got if -znow is not in effect; the first two words
of .got.plt are placed within the relro region.

ld:
	PR ld/30877
	* emulparams/elf32lriscv-defs.sh (DATA_GOT, SEPARATE_GOTPLT):
	Define.
	* emulparams/elf64lriscv-defs.sh (SEPARATE_GOTPLT): Define.
	* testsuite/ld-elf/binutils.exp (binutils_test): Remove riscv*-*-*
	from relro_got expression.