kallsym: use (target - base) to calculate symbol offsets

[SakuraKyuo]

the first symbol is usually _text (which is equal to the kernel base), but on devices without CONFIG_KALLSYMS_ALL=y they will be stripped, thus giving us wrong offsets.

[bmax121]

Thanks, but I think I have fixed it, and it is also compatible with 6.6, you can try it