Fix mis-recognize that Windows-formatted SD card has valid partitions
Fix mis-recognize that Windows-formatted SD card has valid partitions

For Windows-formatted SD card, it is not partitioned (no MBR), but its PBR has the
same boot signature (0xaa55) as MBR. We would easily mis-recognize this SD card has valid
partitions if we only check partition type. We add check by only accepting 0x00 (inactive)
/0x80 (active) for valid partition status.

kjbracey-arm/mbed,mbedmicro/mbed,andcor02/mbed-os,andcor02/mbed-os,andcor02/mbed-os,kjbracey-arm/mbed,andcor02/mbed-os,andcor02/mbed-os,andcor02/mbed-os,kjbracey-arm/mbed,mbedmicro/mbed,mbedmicro/mbed,mbedmicro/mbed,kjbracey-arm/mbed,mbedmicro/mbed