dl/elf: Use format code PRIxGRUB_UINT64_T for 64-bit arg in grub_error()

dl/elf: Use format code PRIxGRUB_UINT64_T for 64-bit arg in grub_error()

The macro ELF_R_TYPE does not change the underlying type. Here its argument
is a 64-bit Elf64_Xword. Make sure the format code matches.

For the RISC-V architecture, rel->r_info could be either Elf32_Xword or
Elf64_Xword depending on if 32 or 64-bit RISC-V is being built. So cast
to 64-bit value regardless.

Signed-off-by: Glenn Washburn <development@efficientek.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>