Makefile.inc: error if UPDATE_IMAGE is enabled with no coreboot.rom

Instead of just failing with the statement:
'mv: cannot stat ‘coreboot.rom’: No such file or directory',
fail with an error that helps the user understand the issue.

Change-Id: Ie693d45710f599991514e0803a7c444636e473c9
Signed-off-by: Martin Roth <martinroth@google.com>
Reviewed-on: https://review.coreboot.org/13065
Tested-by: build bot (Jenkins)
Reviewed-by: Nico Huber <nico.h@gmx.de>
1 file changed