New protocol decoder: ade77xx

libsigrokdecode now supports the ade77xx protocol decoder.

The Analog Devices ADE77xx chips are SPI-based "Poly Phase Multifunction Energy Metering IC with Per Phase Information".

The PD currently decodes register names and values only, more in-depth bit-level decoding can be added later, though.

As usual, there are some example files in sigrok-dumps, test-cases for sigrok-test are pending.

The protocol decoder was contributed by Karl Palsson, thanks a lot!