EDAC, altera: Simplify calculation of total memory

Use of_address_to_resource() and resource_size() instead of manually
parsing the "reg" property from the "memory" node(s).

Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Tested-by: Thor Thayer <thor.thayer@linux.intel.com>
Cc: linux-edac <linux-edac@vger.kernel.org>
Link: http://lkml.kernel.org/r/20170606235500.22772-3-chris.packham@alliedtelesis.co.nz


Signed-off-by: Borislav Petkov <bp@suse.de>