qemu/boards/NETDUINO2: Change heap size to 114k.

This board has 128k RAM, and its heap was originally 120k but commit
e84c9ab changed that to 140k which will
not fit.

This commit reduces the heap down to 114k which allows enough room for the
remaining data/bss, a 10k heap and about 3k spare.

Signed-off-by: Damien George <damien@micropython.org>

Author: dpgeorge

ports/qemu/boards/NETDUINO2/mpconfigboard.mk

@@ -9,4 +9,7 @@ LDSCRIPT = mcu/arm/stm32.ld
 
 SRC_BOARD_O = shared/runtime/gchelper_native.o shared/runtime/gchelper_thumb2.o
 
+# 114k heap, because this board only has 128k RAM and the stack needs 10k.
+MICROPY_HEAP_SIZE ?= 116736
+
 MPY_CROSS_FLAGS += -march=armv7m