fxos8700: Add support for tap and double tap triggers

Adds optional support for tap and double tap sensor triggers to the
fxos8700 driver using the pulse detection hardware function.

Default configuration values were taken from NXP AN4072, section 6.3.
http://cache.nxp.com/assets/documents/data/en/application-notes/AN4072.pdf



Change-Id: Ia95091628a853eb956f6fd1df099a9e6e101b707
Signed-off-by: Maureen Helm <maureen.helm@nxp.com>