sensors: Add handle-to-type mapping in back-compat layer

The result of the old API data_poll is an int, which should represent
a handle to the actualy sensor. That handle must be mapped to the sensor
type, which is required by the new API.

I was wrongly assuming the handle and the type were the same, and that
isn't necessarily true; the only reason this was working is because the
java client API appears to be still doing its own handle-to-type mapping
and mostly ignoring the type value set at the native layer

Change-Id: Ibe6209b91cf96aa885a05d6091155ee7ef929211