Previous to this patch the DMA was setup and then the I2C address sent.
If the I2C address sending failed (eg no I2C device on the bus) then the
DMA was left in an inconsistent state.
This patch moves the DMA setup to after a successful sending of the I2C
address(es).
See issue #1765.
This is in preparation for supporting other MCU series, such as
STM32F2xx. Directory structure for the HAL is now hal/f4/{inc,src},
where "f4" will in the future be different for other series.
HAL source/header files that are not use are removed to reduce the size
of the code.
