Make external target detection less restrictive

Switch to external or shield if VCC or GNDdetect are detected.
Requiring both to be detected would reduce the number of targets that can be debugged

Author: mbrossard

source/board/nrf5x_dk_ext.c

@@ -155,12 +155,12 @@ static void nrf_prerun_board_config(void)
     // nonzero if external target is detected
     bit1 = (PIOB->PIO_PDSR >> 6) & 1;  // Read PB6
     bit2 = (PIOB->PIO_PDSR >> 18) & 1; // Read PB18
-    target_ext = bit1 & !bit2;
+    target_ext = bit1 | !bit2;
 
     // nonzero if shield-mounted target is detected
     bit1 = (PIOB->PIO_PDSR >> 5) & 1;  // Read PB5
     bit2 = (PIOB->PIO_PDSR >> 23) & 1; // Read PB23
-    target_shield = bit1 & !bit2;
+    target_shield = bit1 | !bit2;
 
     // Disable pull-ups for detection
     PIOB->PIO_PUDR = (1 << 18); // pull-up disable