Few questions about freeing MXP I2C port

[kjaget]

I don't have a test case so I'm not 100% positive on these, hence questions rather than statements.

allwpilib/hal/src/main/native/athena/I2C.cpp

Line 184 in 11fb0a4

if (i2CMXPObjCount-- == 0) {

It looks like the highlighted code should be a pre-decrement, or maybe a compare against 1 instead of 0? Same potential issue with the case for the onboard port.

Also, should the HAL_FreeDIOPort() calls be inside the if() block here - seems like releasing them when objCount>0 might be wrong.

Might also be good to have a check that count isn't already 0 before decrementing?

[PeterJohnson]

Will be fixed by #2676.