ARM: dts: aspeed: ast2600evb: Add phase correction for emmc controller.

Set MMC timing-phase register by adding the phase correction binding in the
device tree.

Signed-off-by: Steven Lee <steven_lee@aspeedtech.com>
Acked-by: Andrew Jeffery <andrew@aj.id.au>
Reviewed-by: Joel Stanley <joel@jms.id.au>
Link: https://lore.kernel.org/r/20210524073308.9328-3-steven_lee@aspeedtech.com


Signed-off-by: Joel Stanley <joel@jms.id.au>