ARM: dts: aspeed-g5: Use recommended generic node name for SDMC

The EDAC is a sub-function of the SDRAM Memory Controller. Rename the
node to the appropriate generic node name.

Cc: Stefan M Schaeckeler <sschaeck@cisco.com>
Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Reviewed-by: Joel Stanley <joel@jms.id.au>
Reviewed-by: Stefan Schaeckeler <sschaeck@cisco.com>
Signed-off-by: Joel Stanley <joel@jms.id.au>