dt-bindings: i2c: mv64xxx: Add Allwinner A523 compatible string

The I2C controller IP used in the Allwinner A523/T527 SoCs is
compatible with the ones used in the other recent Allwinner SoCs.

Add the A523 specific compatible string to the list of existing names
falling back to the allwinner,sun8i-v536-i2c string.

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Andi Shyti <andi.shyti@kernel.org>
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>