pbl: support panic with log output ...

If panic is called with a string in the PBL, print the panic string
before falling into the busy loop.

Signed-off-by: Rouven Czerwinski <r.czerwinski@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

pbl: remove start_barebox() stub ...

PBL never calls start_barebox().  If it does, it is a bug.
Without this stub function, we can detect such a bug at link time.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

startup: add __noreturn to start_barebox ...

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

pbl: provide hang() function for the pbl ...

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

Add pre-bootloader (pbl) image support ...

This allows for creating a pre-bootloader binary for
 - nand boot
 - mmc boot
 - compressed image

The pbl will be incharge of the lowlevel init if needed.
The barebox will skip it.

Import string functions from linux 3.4 (arch/arm/boot/compressed/string.c) and
implement a dummy panic.

For now on introduce dummy zbarebox* targets and c code that will contain later
the decompressor. This only implemeted on ARM.

This patch is based on Sascha Hauer <s.hauer@pengutronix.de>
Add compressed image support patch

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>