dt-bindings: edac: aspeed-sdram-edac: Add ast2400/ast2600 support

Add Aspeed AST2400 and AST2600 binding for the Aspeed EDAC driver.

Signed-off-by: Troy Lee <troy_lee@aspeedtech.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Acked-by: Joel Stanley <joel@jms.id.au>
Link: https://lkml.kernel.org/r/20201207090013.14145-1-troy_lee@aspeedtech.com