Raspberry pi CM4 support

[dolfje]

I'm busy with trying piduino for the Raspberry Pi CM4.

From what I read, it is almost the same as Raspberry 4b.
So I'm trying to get it working.

I have already updated the database to the following:

board:
54|RaspberryPi Compute Module 4 (0xb03140)|2048|1.0|24|3|1|1|0|0
board_family:
24|RaspberryPi Compute Module 4|0|5
revision:
54|11546944

Now busy with checking if this works. So will update when I find incompatibilities.

[dolfje]

The CM4 has 5 serial ports, so

piduino/include/piduino/arduino/HardwareSerial.h

Line 112 in 8b79109

static const int numberOfPorts = 4;

has to be changed.