Fix Arduino.h `portOutputRegister()` and `portModeRegister()`

[carlosperate]

These functions were using the OUTSET and DIRSET registers instead of OUT and DIR. The SET version of these registers only do something when a "1" is written to any of their bits, writting a "0" does nothing.

From the nRF52833 datasheet:

Found this issue when using some of the Adafruit libraries using a BUSIO_USE_FAST_PINIO macro that enables utilisation of these functions, and noticed that some of the pins were not being driven low, only high. Using this patch locally fixed the issue.

[carlosperate]

For comparison I've also found these other nRF cores using the registers from this PR:

• https://github.com/adafruit/Adafruit_nRF52_Arduino/blob/1.3.0/cores/nRF5/Arduino.h#L148-L151
• https://github.com/arduino/ArduinoCore-primo/blob/1.0.1/variants/arduino_primo/variant.h#L67-L69
• https://github.com/particle-iot/device-os/blob/v3.3.0/user/inc/Arduino.h#L108-L118

So that should give us some confidence as well.