mimxrt/boards/TEENSY40: Re-create the flash FS after deploy.

This is required since the Teensy Halfkay loader attempts to erase all of
the flash but fails to do so, at least in my tests.  Formatting brings it
back to a known state.

ports/mimxrt/Makefile

@@ -2,6 +2,8 @@ BOARD ?= TEENSY40
 BOARD_DIR ?= boards/$(BOARD)
 BUILD ?= build-$(BOARD)
 
+PORT ?= /dev/ttyACM0
+
 CROSS_COMPILE ?= arm-none-eabi-
 
 ifeq ($(wildcard $(BOARD_DIR)/.),)

ports/mimxrt/boards/TEENSY40/format.py

@@ -0,0 +1,11 @@
+# format.py
+# Re-create the file system
+
+import os
+import mimxrt
+
+bdev = mimxrt.Flash()
+
+os.VfsLfs2.mkfs(bdev, progsize=256)
+vfs = os.VfsLfs2(bdev, progsize=256)
+os.mount(vfs, "/")

ports/mimxrt/boards/TEENSY40/mpconfigboard.mk

@@ -3,3 +3,5 @@ MCU_VARIANT = MIMXRT1062DVJ6A
 
 deploy: $(BUILD)/firmware.hex
 	teensy_loader_cli --mcu=imxrt1062 -v -w $<
+	sleep 1
+	$(PYTHON) $(TOP)/tools/pyboard.py --device $(PORT) $(BOARD_DIR)/format.py