dm: Reduce SPL device tree size

dm: Reduce SPL device tree size

The SPL device tree size must be minimised to save memory. Only include
properties that are needed by SPL - this is determined by the presence
of the "u-boot,dm-pre-reloc" property. Also remove a predefined list of
unused properties from the nodes that remain.

Signed-off-by: Simon Glass <sjg@chromium.org>