uboot-phytec

misc: fs_loader: Replace label with DT phandle

In previously label which will be expanded to the node's full path was
used, and now replacing label with most commonly used DT phandle. The
codes were changed accordingly to the use of DT phandle and supporting
multiple instances.

Signed-off-by: Tien Fong Chee <tien.fong.chee@intel.com>