Also make sure they are non-negative.
This is not documented in Mifare Classic spec, but based on findings from NXP:
- Operand should be stored in little-endian format in the transceive buffer
- Tag ignores the sign bit on the operand, its effectively 31-bit unsigned
- Overflow and underflow generates an error.
Change-Id: Id3389b3894ded732c4b00d564ca53f5df651359e
b134223f91