HACK: libsensors: First attempt at using Inv IIO MPU6050+AK8963

This is just a starting point to see how the new
hardware/invensense/sensors_iio integrates.

The patch needs
  https://android-git.corp.google.com/g/#/c/200993/
and the poll loop is based on the sensors_mpl.c.

The way the sensor polling works is messy. I don't yet fully understand
how the read*Events() messes around with data and nb.
But it does allow pressure/light to work with gyro/compass/accel.

The Android.mk only builds for manta because:
  - sensors.manta needs to link against the invensense/sensors_iio's
     libinvensense_hal
  - weirdly, the build always builds devices that are not selected.
  - the invensense/sensors_iio produces files that conflict with
      those produced by invensense/{sensors,mlsdk} used by non-manta devices.
  - only one of the invensense/sensors* can be built.
Without the restriction, sensors.manta fails to link against the non-manta
 libinvensense_hal duiring a non-manta build.

Change-Id: I9841d0d48c9792e8adc7b079cbcd9c4d82e2be88
3 files changed