ARM: zynq: switch to multi-image build ...

Finally move over to a multi-image based build.

Signed-off-by: Lucas Stach <dev@lynxeye.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

ARM: zynq: move header generation to zynq_mkimage ...

Instead of generating a suitable image header with linker magic, move
all of this into zynq_mkimage. The configuration file format and parsing
is based on imx-image. This gets us one step further on the road to
proper multi-image support.

Signed-off-by: Lucas Stach <dev@lynxeye.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

ARM: zynq: use getopt in zynq_mkimage ...

Makes extending the command line much easier.

Signed-off-by: Lucas Stach <dev@lynxeye.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

ARM: zynq: add trivial image build mechanism ...

Currently this just calls the zynq_mkimage script to stamp in the header
checksum. Can be extended to a proper multi-image build later on.

This requires a PBL to be build, but as the only supported Zynq board
already selects the PBL option in the defconfig there is no big change
to the previous status

Signed-off-by: Lucas Stach <dev@lynxeye.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>