DRV2605 haptic driver PR

[Jacob Rosenthal <ja...@gmail.com>]

Ive got a drv2605 haptic motor driver PR in for comments at
https://github.com/apache/mynewt-core/pull/757

I think I should develop a config struct for it..though that said theres
quite a lot of configuration setup thats motor and thus bsp specific so Im
somewhat happy with my clunk sysval setup atm.. Comments welcome

Its also really kinda specific to LRA motors as thats what Im using, it
could use a bit of generalizing for erm motors, though I think its wierd to
use such a capable chip for ERMs so Im not going to put much work in there
unless theres an outpouring of support for it.

Also Im using the sensor api even though im not in the sensors folder nor
is an actuator a sensor because as weve talked about before the interface
pattern is much cleaner.

Any other comments welcome.