update instructions for use with rpi4 and 1.6 revision motherboard

[MarioMasta64]

update instructions for use with rpi4 and 1.6

the pinout for 1.6 is the same however the window for messing with the eeprom is basically "run program then power on console" since the system usually turns off soon after turning on

removed the part about 1.6 needing extra connections that are tricky (this is referring to an lpc rebuild which is not actually required for eeprom management.)

i added the bcm source for rpi4 the compile instructions for 3 and 4 are the same besides the file used