deprecate gumstix aerocore - no longer supported by mfg

.ci/Jenkinsfile-compile

Makefile

README.md

boards/gumstix/aerocore2/default.cmake

boards/gumstix/aerocore2/firmware.prototype

boards/gumstix/aerocore2/init/rc.board_defaults

boards/gumstix/aerocore2/init/rc.board_sensors

boards/gumstix/aerocore2/nuttx-config/Kconfig

boards/gumstix/aerocore2/nuttx-config/include/board.h

boards/gumstix/aerocore2/nuttx-config/nsh/defconfig

boards/gumstix/aerocore2/nuttx-config/scripts/ld.script

boards/gumstix/aerocore2/src/CMakeLists.txt

boards/gumstix/aerocore2/src/board_config.h

boards/gumstix/aerocore2/src/can.c

boards/gumstix/aerocore2/src/init.c

boards/gumstix/aerocore2/src/led.c

boards/gumstix/aerocore2/src/spi.c

boards/gumstix/aerocore2/src/timer_config.c

boards/gumstix/aerocore2/src/usb.c