merge from Develop

[hathach]

• Fixed PWM psel[1] is not reset
• Fixed Hardcoded RXD/TXD pin #41 move RXD, TXD into board header
• Added Metro nRF52840 Rev A
• Fixed Fix OTA using nRF toolbox on iPhone (tested on SE and XS) #40 OTA issue with BLE_GAP_EVT_PHY_UPDATE_REQUEST e.g connecting with iPhone X

[dhalbert]

Thanks! The code changes all look good. I built and loaded on a Feather 52840 and a PCA10056. Uploaded using the Makefile targets and J-Link. Also reloaded SD. Both boards worked fine with the new bootloader. I was able to load CircuitPython, and did a BLE test and it's working.

I did not test the OTA update.

[hathach]

thanks @dhalbert for testing this out. OTA should work as before, this fixes an issue with latest central such as iPhone X which is capable of 2M Phy and requesting nrf52840 to negotiate.