* AD7768_zed: Fix wideband filter bug
In SPI control mode, when not used as GPIO the FILTER pin and when a
crystal is used as the clock source, this pin must be set to 1.
The START pin must be tied to a logic 1 through a pull-up resistor, when
it is not used.
Removes a lot of boilerplate code.
Using the new scheme it is possible to add new projects or sub-projects
without having to re-generate any existing Makefiles.
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>