lib: optee: migration optee_copy_fdt_nodes for OF_LIVE support

lib: optee: migration optee_copy_fdt_nodes for OF_LIVE support

The optee_copy_fdt_nodes is only used to copy op-tee nodes
of U-Boot device tree (from gd->fdt_blob when OF_LIVE is not activated)
to external device tree but it is not compatible with OF_LIVE.

This patch migrates all used function fdt_ functions to read node on
old_blob to ofnode functions, compatible with OF_LIVE and remove this
parameter "old_blob".

The generated "device tree" is checked on stm32mp platform with OF_LIVE
activated.

Signed-off-by: Patrick Delaunay <patrick.delaunay@foss.st.com>