riscv: select ARCH_WANT_LD_ORPHAN_WARN for !XIP_KERNEL

riscv: select ARCH_WANT_LD_ORPHAN_WARN for !XIP_KERNEL

Now, after that all the sections are explicitly described and
declared in vmlinux.lds.S, we can enable ld orphan warnings for
!XIP_KERNEL to prevent from missing any new sections in future.

Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20230119155417.2600-6-jszhang@kernel.org
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>