variants: XIAO NRF52: Enable button pullup

Some versions of the Wio-SX1262 board don't have the button and the
pullup resistor populated. Enable the internal pullup to prevent
a floating pin and spurious button presses on those boards.

This fixes #1173.

Signed-off-by: Frieder Schrempf <[email protected]>

variants/xiao_nrf52/XiaoNrf52Board.cpp

@@ -38,7 +38,7 @@ void XiaoNrf52Board::begin() {
   digitalWrite(VBAT_ENABLE, HIGH);
 
 #ifdef PIN_USER_BTN
-  pinMode(PIN_USER_BTN, INPUT);
+  pinMode(PIN_USER_BTN, INPUT_PULLUP);
 #endif
 
 #if defined(PIN_WIRE_SDA) && defined(PIN_WIRE_SCL)