Fix possible overflow or error in driver sub-system allocation

[LuernOutOfOrder]

On the refactor of the static driver allocation, I spotted a bug when changing the size of the serial sub-system, passing from 4 to 2 cause exception to happened; like possible overflow. Keeping it to 4 make the memory layout less enclins to crush important data live vtable ptr or things like that.

So, need to fix the allocation of sub-system to make the init and basic allocation using the static in config file to work; like I only have one serial, so 2 might just work as well as 4 as a max sub-system size.

if serial sub-system size is set to 0,1,2, 5, 6, 7, 8, it make the kernel crash or just UB.