With multiboard support the compiletime generated BOARDINFO string
gets more and more meaningless. This removes it from Kconfig and
replaces it with a variable that can be set at boardlevel.

Also many boards have a standard setting for the hostname in the
environment. This patch also moves the standard to C code by calling
barebox_set_hostname().

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

this will allow to have boot sequence and later to use PXE

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Cc: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>