Move the code responsible for installing stage3.bin to the
boot/Makefile. In addition, remove the stage3.bin from the Makefile
`all` target prerequisites in src/Makefile, as zipl can be built without
it. While at it, use $(INSTALL) instead of $(CP) for the bootloader
installation.
Reviewed-by: Steffen Eiden <seiden@linux.ibm.com>
Signed-off-by: Marc Hartmayer <mhartmay@linux.ibm.com>
Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>