kernel-install: Add missing error messages

In some cases kernel-install can fail without printing anything. Add
error messages for these cases.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
dlmalloc: fix compiler warning

This patch fix a compiler warning while building sandbox barebox with
gcc version 4.8.2.

common/dlmalloc.c: In function ‘barebox_calloc’:
common/dlmalloc.c:1756:2: warning: ISO C90 forbids mixed declarations
and code [-Wdeclaration-after-statement]
  void *mem = malloc(sz);
  ^

Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Release v2013.11.0

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