Add stub boot code for ARM for creating filesystem images

[DrDeano]

Currently when creating the FAT32 and MBR boot sectors, a stub x86 boot code is used to say that the image is non bootable. The current x86 version (with the asm code) can be found in the kernel/arch/common.

There needs to be an ARM version. All the code will need to do it print to the screen saying the image in not bootable and be a valid boot sector.