The 'msba2' common files have accumulated many empty files are files that
do nothing.
This makes reasoning about the boards needlessly difficult.
Trim down on `common/msba2/` so that it now only contains the setup for the
UART/bootloader based flashing.
This should eventuelly be moved to `makefiles/tools/`
- Replaced magic numbers in the CC110X configuration of the MSBA2
with SPI_DEV(x) and GPIO_PIN(x, y) macros
- Adjusted implementation of `cc110x_params.h` to match the code of `at86rf2xx`
- Made MSBA2's CC110X parameters the default configuration
