add goldfish_sensors: basic support for pipe based acceleration support

This imports a small chunk of the old hw-sensors code to handle the
acceleration code. The old code "supported" a bunch of different sensors
however I've dropped all the boilerplate for that. Any potential
upstream solution will probably want to enumerate things differently.

Apart from only supporting the accelerometer this also interfaces
directly with the AndroidPipe code instead of going through the qemud
layer. It also requires the updated guest code.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
ranchu: do set_rotation for accelerometer