aspeed: Tune eMMC device properties to reflect HW strapping

aspeed: Tune eMMC device properties to reflect HW strapping

When the boot-from-eMMC HW strapping bit is set, use the 'boot-config'
property to set the boot config register to boot from the first boot
area partition of the eMMC device. Also set the boot partition size
of the device.

Signed-off-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: Andrew Jeffery <andrew@codeconstruct.com.au>
Tested-by: Andrew Jeffery <andrew@codeconstruct.com.au>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Tested-by: Philippe Mathieu-Daudé <philmd@linaro.org>