asm-generic: Always define Elf_Rel and Elf_Rela

These definitions are useful for relocating the kernel image as well,
regardless of the type of relocations used for modules.

Signed-off-by: Samuel Holland <samuel.holland@sifive.com>
Link: https://lore.kernel.org/r/20241026171441.3047904-5-samuel.holland@sifive.com


Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>