arm: dts: Add Altera SDRAM EDAC bindings & devicetree entries.

Add the Altera SDRAM EDAC bindings and device tree changes to the Altera SoC
project.

There was a discussion thread on whether this driver should be an mfd driver
or just make use of syscon, which is already a mfd. Ultimately, the
decision to use a simple syscon interface was reached.[1]

[1] https://lkml.org/lkml/2014/7/30/514

Signed-off-by: Thor Thayer <tthayer@opensource.altera.com>
Acked-by: Pavel Machek <pavel@denx.de>
[dinguyen] cleaned-up commit header and remove version history.
Signed-off-by: Dinh Nguyen <dinguyen@opensource.altera.com>