bricks/primehub: increase heap to 256K

This still leaves 64K for static/global variables and stack.

Issue #19

Author: dlech

bricks/primehub/mpconfigport.h

@@ -6,7 +6,7 @@
 #define MICROPY_HW_BOARD_NAME           "SPIKE Prime Hub"
 #define MICROPY_HW_MCU_NAME             "STM32F413VG"
 
-#define PYBRICKS_HEAP_KB                64 // half of RAM
+#define PYBRICKS_HEAP_KB                256
 
 #define PYBRICKS_HUB_PRIMEHUB           (1)