version: add missing EXPORT_SYMBOL for version_string ...

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

Makefile: fix build timestamps ...

This patch adds the scripts/mkcompile_h from the Kernel. This gives
us additional information about the build like who built this binary
and with which compiler. Currently the only information used is the
build timestamp and the generation number.
This also fixes the build timestamp in the banner which is now correct
even with consecutive builds without making clean in between.

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

remove EARLY_INIT and EARLY_CONSOLE support ...

Bitrotted over time and nearly unused, so remove it.

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

move version_string to seperate file ...

In a noninteractive environment barebox will be compiled without
command support. So move version_string to a seperate file which
is compiled unconditionally.
Also, display the banner when the simple console support is used.

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