riscv: annotate check_unaligned_access_boot_cpu() with __init

This function is solely called as an initcall, thus annotate it with
__init.

Signed-off-by: Clément Léger <cleger@rivosinc.com>
Reviewed-by: Evan Green <evan@rivosinc.com>
Link: https://lore.kernel.org/r/20231004151405.521596-7-cleger@rivosinc.com


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