Arduino.h: Allow including from other headers

- I was facing some problems due to multiple declarations of
  arduino_pins array.
- It is important for Arduino.h to be includable from both C and C++
  code since `Common.h` defines some data types like PinStatus and
  PinMode

Signed-off-by: Ayush Singh <[email protected]>

Author: Ayush1325

cores/arduino/Arduino.h

@@ -87,9 +87,6 @@ enum digitalPins {
 	NUM_OF_DIGITAL_PINS
 };
 
-const struct gpio_dt_spec arduino_pins[] = {DT_FOREACH_PROP_ELEM_SEP(
-	DT_PATH(zephyr_user), digital_pin_gpios, GPIO_DT_SPEC_GET_BY_IDX, (, ))};
-
 #ifdef CONFIG_ADC
 
 #define AN_ENUMS(n, p, i) A ## i = DIGITAL_PIN_GPIOS_FIND_PIN( \
@@ -101,5 +98,7 @@ enum analogPins { DT_FOREACH_PROP_ELEM(DT_PATH(zephyr_user),
 #endif
 
 #include <variants.h>
+#ifdef __cplusplus
 #include <zephyrPrint.h>
 #include <zephyrSerial.h>
+#endif // __cplusplus

cores/arduino/zephyrCommon.cpp

@@ -6,6 +6,9 @@
 
 #include <Arduino.h>
 
+static const struct gpio_dt_spec arduino_pins[] = {DT_FOREACH_PROP_ELEM_SEP(
+	DT_PATH(zephyr_user), digital_pin_gpios, GPIO_DT_SPEC_GET_BY_IDX, (, ))};
+
 namespace {
 
 /*