powerpc: dts: t1024rdb: tag serial nodes with bootph-all

Make sure the serial driver is initialized before relocation by tagging
the serial nodes with "bootph-all". Add these u-boot specific properties
to an *-u-boot.dtsi file.

Signed-off-by: Camelia Groza <camelia.groza@nxp.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>