ulink_calculate_delay() function

OpenULINK TCK frequency helper functions ***************** Calculate delay values for a given TCK frequency. The OpenULINK firmware uses five different speed values for different commands. These speed values are calculated in these functions. The five different commands which support variable TCK frequency are implemented twice in the firmware: 1. Maximum possible frequency without any artificial delay 2. Variable frequency with artificial linear delay loop To set the ULINK to maximum frequency, it is only necessary to use the corresponding command IDs. To set the ULINK to a lower frequency, the delay loop top values have to be calculated first. Then, a CMD_CONFIGURE_TCK_FREQ command needs to be sent to the ULINK device. The delay values are described by linear equations: t = k * x + d (t = period, k = constant, x = delay value, d = constant) Thus, the delay can be calculated as in the following equation: x = (t - d) / k The constants in these equations have been determined and validated by measuring the frequency resulting from different delay values.