[PATCH v2] mfd: add TPS6586x driver

[Mike Rapoport]

 Hi Samuel.
Here's the updated version of the TPS6586x driver.
I've left the GPIO code in the driver because of
* David prefers to keep GPIO part of MFD devices in the drivers/mfd ( [1] )
* Implementation of dedicated input functionality rather belongs to the MFD core

[1] http://lkml.org/lkml/2010/6/30/307


v2 changes: changed tps6586x_{probe,remove} to  tps6586x_i2c_{probe,remove}
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