Return true if the efuse is readable by software

def is_readable(self):
        """ Return true if the efuse is readable by software """
        if self.read_disable_bit is None:
            return True  # read cannot be disabled
        value = (self.parent.read_efuse(0) >> 16) & 0xF  # RD_DIS values
        return (value & (1 << self.read_disable_bit)) == 0