These new build targets will construct a flash image that
includes both a bootloader as well as a firmware image all
in one. Examples:
make ef_coptercontrol
make ef_revolution
This also adds support for a new target for writing this EF
image to boards that support a DFU interface (only F4-based
boards). This can be done by running:
make dfuutil_install
# Boot board with SBL asserted to activate STM32 DFU ROM
# Attach USB cable
make ef_revolution_dfu
Bootloader images are also now padded out to occupy the full
BL flash region.
