pycubed: add trailing newline to file

POSIX specifies that text files end in a trailing newline

Author: jepler

ports/atmel-samd/boards/pycubed/mpconfigboard.mk

@@ -21,4 +21,4 @@ CIRCUITPY_PS2IO = 0
 FROZEN_MPY_DIRS += $(TOP)/frozen/Adafruit_CircuitPython_BusDevice
 FROZEN_MPY_DIRS += $(TOP)/frozen/Adafruit_CircuitPython_NeoPixel
 FROZEN_MPY_DIRS += $(TOP)/frozen/Adafruit_CircuitPython_Register
-FROZEN_MPY_DIRS += $(TOP)/frozen/Adafruit_CircuitPython_SD
+FROZEN_MPY_DIRS += $(TOP)/frozen/Adafruit_CircuitPython_SD