[PATCH v6] AT91: Add a driver for the ADC

[Maxime Ripard]

Hi all,

This patchset adds the driver for the ADC in the AT91 SoC. It has been tested on
the at91sam9g20ek and should work on sam9g45 as well.

For now, it only reads values when asked for by sysfs, but eventually will
support hardware triggers and more boards.

This patchset is based on the "[PATCH 0/6 V2] IIO: Out of staging step 1: The
core" patchset from Jonathan Cameron, applied on top of 3.1

Improvements from v5:
  - Don't run the SoC specific code if the driver is not selected in the
configuration
  - Fix the waitqueue timeout error handling to have a more sensible behaviour
  - Minor cosmetic improvements

Cc: Nicolas Ferre <nicolas.ferre at atmel.com>
Cc: Patrice Vilchez <patrice.vilchez at atmel.com>
Cc: Thomas Petazzoni <thomas.petazzoni at free-electrons.com>