drivers: edac: Add Synopsys EDAC driver

Add an EDAC driver for the Synopsys DDR memory controller, used in the
Xilinx MPSoC (ZynqMP) devices, to allow monitoring for ECC errors.

Note that currently only the compatible string used for the ZynqMP
(shared with Linux) is currently supported. Support for other Synopsys
core implementations can be added in the future.

Signed-off-by: Robert Hancock <robert.hancock@calian.com>