winrt: Avoid divide-by-zero when starting sensors

Several sensors were setting the dataRate without checking the value
first. If the dataRate is zero, then don't set the native rate (use
the default).

Task-number: QTBUG-40664
Change-Id: I50e78fd071bd1f56e47baf23b74900b8a6e6c7eb
Reviewed-by: Maurice Kalinowski <maurice.kalinowski@digia.com>