pinmux: Move the Arduino 101 board to the pinmux model

This driver doesn't provide any API, it only initializes the pinmux
controller to appropriate values depending on the board.

The first board to use this new infrastructure is the Arduino 101 board,
because it is alphabetically the first.

To better organize code for the different SoCs and boards, a "family"
level is created in the 'drivers/pinmux' directory. The Arduino 101
board is part of the Quark MCU "family".

The PINMUX_DEV configuration (and functionality) is removed for now, it
will be added back when the pinmux_dev drivers are (re)introduced, with
clearer semantics.

Change-Id: Idf5cc3caf6be620aa50828ae8fdc535df6caf458
Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>