fdtgrep: propagating the bootph-* properties to parent nodes during build time.

Currently bootph-* is parsed by fdtgrep for packing all the parent nodes in U-boot DT but bootph-* is not implied on the parent nodes, bootph-* has some significance that helps in driver probing as well and by not propagating them to parents, driver models can be broken by just keeping them in the child nodes. Refer 0 for more discussion