The method was changed, but not for the CSx pins. No functional change.

OCOTP_Init() has been removed from mphalport.c. The library files
are missing for the MIMXRT1015, and for just reading the OCOTP
the Init is not required.

Sometimes frames could not be sent immediately because the controller
was still busy with previous frames. Then, an error was returned to
lwip. This fix adds a limited number of retries for this busy state,
waiting 100µs before the next attempt. Typically the transmit succeeds
now at the second attempt.

Second change: Reset the controller for a clean state after soft reset.

Teensy 4.1 used different pins for SPI1 than Teensy 4.0. That
caused irrtitations. So I propose to change it.

If the board directory contains a manifest.py file, it will be
included. File not found errors will be ignored.

That caused Ethernet to lock up at high data rates after ~200MByte
data average in a row. Tested now with data bursts up to 10 GByte and
overall data rates of ~8MByte/s at the Eth100 port.

- Ensure the symmetry of PWM.
  The duty rate of X and Q channels was not 50%, when it should have been.
  That is evident at high frequencies, like 15Mhz of 37.5 MHz. At low
  frequencies the deviation mattered less. The A/B channels were fine.
- Round up or down non-integer division factors. Before, always the
  floor value was used.