AP_HAL_PX4: standardize inclusion of libaries headers

Do the missing header changes due to changing the code before the pr
getting accepted.

libraries/AP_HAL_PX4/UARTDriver.cpp

@@ -16,7 +16,7 @@
 #include <termios.h>
 #include <drivers/drv_hrt.h>
 #include <assert.h>
-#include "../AP_HAL/utility/RingBuffer.h"
+#include <AP_HAL/utility/RingBuffer.h>
 #include "GPIO.h"
 
 using namespace PX4;