fix(tmt): Fix roundtrip failure for single character mxint8 attribute values
Enable "0x" prefix to represent mxint8 values.
Roundtrip serialization failed when an mxint8 attribute had a single-character string value (e.g., "0x7"). The serializer previously assumed a 2-character width and raised an error. Updated logic to handle both.
Modified template generation script to have "0x0" string for mxint8 type.
Signed-off-by: Yuvaraj Venkatesh yuvaraj.venkatesh@arm.com