The Makefile compression commands all append the size of the
uncompressed image. With CONFIG_IMAGE_COMPRESSION_NONE simply
'shipped' is used which does not append the size. Add and use
a special comp_copy function which adds the size. This helps
us to get the uncompressed image size in the startup code later.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>