Fix bug that breaks RS485 on the Opta

[alrvid]

PB14 is used to enable USB on the PMC, but it is used for RS485 on the Opta. Therefore, performing automatic detection on the Opta breaks RS485.

[github-actions]

Memory usage change @ d955b69

Board	flash	%	RAM for global variables	%
arduino:mbed_portenta:envie_m7	N/A	N/A	N/A	N/A
arduino:renesas_portenta:portenta_c33	0 - 0	0.0 - 0.0	0 - 0	0.0 - 0.0

Click for full report table

Board	examples/SD_Card_Example flash	%	examples/SD_Card_Example RAM for global variables	%	examples/USB_Hotplug_Example flash	%	examples/USB_Hotplug_Example RAM for global variables	%	examples/USB_No_Hotplug_Example flash	%	examples/USB_No_Hotplug_Example RAM for global variables	%
arduino:mbed_portenta:envie_m7	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A	N/A
arduino:renesas_portenta:portenta_c33	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0	0	0.0

Click for full report CSV

Board,examples/SD_Card_Example<br>flash,%,examples/SD_Card_Example<br>RAM for global variables,%,examples/USB_Hotplug_Example<br>flash,%,examples/USB_Hotplug_Example<br>RAM for global variables,%,examples/USB_No_Hotplug_Example<br>flash,%,examples/USB_No_Hotplug_Example<br>RAM for global variables,%
arduino:mbed_portenta:envie_m7,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A,N/A
arduino:renesas_portenta:portenta_c33,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0