fdisk(8): Make -A preserve BIOS boot partition

fdisk(8): Make -A preserve BIOS boot partition

On PolarFire SoC, the HSS firmware loads HSS payload from BIOS boot
partition. Typically the payload carries second-stage low-level boot
code, such as U-Boot. If the payload is missing, the SoC is not able
to boot normally. Hence automatic disk formatting should not delete
the partition.

OK krw@