* Diff reduction between ADNS9800 and PMW3360 drivers.
They are very similar devices. This (somewhat) unreadable diff is
essentially a no-op, but it makes a `vimdiff` between the 2 drivers much
more readable.
* Cleanup pwm3360 driver some more.
Remove redundant calls to spi_start() and spi_stop(), as pmw3360_write()
will already call these.
