uart: make mraa_uart_get_dev_path return const char*

Signed-off-by: Brendan Le Foll <brendan.le.foll@intel.com>

api/mraa/uart.h

@@ -125,7 +125,7 @@ mraa_result_t mraa_uart_set_timeout(mraa_uart_context dev, int read, int write,
  * @param dev uart context
  * @return char pointer of device path
  */
-char* mraa_uart_get_dev_path(mraa_uart_context dev);
+const char* mraa_uart_get_dev_path(mraa_uart_context dev);
 
 /**
  * Destroy a mraa_uart_context

include/mraa_internal_types.h

@@ -91,7 +91,7 @@ struct _aio {
 struct _uart {
     /*@{*/
     int index; /**< the uart index, as known to the os. */
-    char* path; /**< the uart device path. */
+    const char* path; /**< the uart device path. */
     int fd; /**< file descriptor for device. */
     /*@}*/
 };

src/uart/uart.c

@@ -404,7 +404,7 @@ mraa_uart_set_timeout(mraa_uart_context dev, int read, int write, int interchar)
     return MRAA_ERROR_FEATURE_NOT_IMPLEMENTED;
 }
 
-char*
+const char*
 mraa_uart_get_dev_path(mraa_uart_context dev)
 {
     if (!dev) {