Update RISC-V relocations

Update RISC-V relocations

Update the list of RISC-V relocations from the ELF psABI as of June 2024.
It removes binutils-internal only relocations that were never part of
actual object files.  The GNU_VTINHERIT and GNU_VTENTRY relocations were
never used because the corresponding GCC option -fvtable-gc was never
supported on RISC-V.