add bootloader

Author: ladyada

boards.txt

@@ -1351,7 +1351,7 @@ adafruit_matrixportal_m4.build.variant_system_lib=
 adafruit_matrixportal_m4.build.vid=0x239A
 adafruit_matrixportal_m4.build.pid=0x80C9
 adafruit_matrixportal_m4.bootloader.tool=openocd
-adafruit_matrixportal_m4.bootloader.file=featherM4/bootloader-feather_m4-v2.0.0-adafruit.5.bin
+adafruit_matrixportal_m4.bootloader.file=matrixportalM4/bootloader-matrixportal_m4.bin
 adafruit_matrixportal_m4.compiler.arm.cmsis.ldflags="-L{runtime.tools.CMSIS-5.4.0.path}/CMSIS/Lib/GCC/" "-L{build.variant.path}" -larm_cortexM4lf_math -mfloat-abi=hard -mfpu=fpv4-sp-d16
 adafruit_matrixportal_m4.menu.cache.on=Enabled
 adafruit_matrixportal_m4.menu.cache.on.build.cache_flags=-DENABLE_CACHE