Analog driver updates (incomplete).

Various updates for the "analog" driver -- currently just for the "ev3dev_analog" misc device interface (device 1).  The other two (device 2 == test-pin, device 3 == DCM) still to be dealt with.  Mostly compiled, but needs SPI stuff tying in with the spi_davinci stuff that has the SPI I/O ports (should be a case of writing a suitable spi_board_info thing).