RISC-V: Moved out linker internal relocations after R_RISCV_max.

RISC-V: Moved out linker internal relocations after R_RISCV_max.

Just the lightest modifications about this, without any further checks and
considering --emit-relocs.  We will need to improve it in the future, but
first do this to avoid conflicts between linker internal relocations and the
new definition of psabi.  For example, TLSDESC relocs.

Passed riscv-gnu-toolchain regressions, so should be safe enough to commit.

Co-authored-by: Tsukasa OI <research_trasio@irq.a4lg.com>
bfd/
	* reloc.c: Removed linker internal relocations.
	* bfd-in2.h: Regenerated.
	* libbfd.h: Regenerated.
	* elfnn-riscv.c: Defined R_RISCV_DELETE in include/elf/riscv.h.
	* elfxx-riscv.c (howto_table, howto_table_internal): Moved linker
	internal relocations from howto_table into howto_table_internal.
	(riscv_reloc_map): Removed linker internal relocations mapping.
	(riscv_elf_rtype_to_howto): Return howto of linker internal
	relocations from howto_table_internal.
include/
	* elf/riscv.h: Defined linker internal relocations after R_RISCV_max.