x86/boot: Close opened file descriptor

During build we open a file, read that but do not close it. Fix
that by sticking fclose() at the right place.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: http://lkml.kernel.org/r/1371628383-11216-1-git-send-email-jslaby@suse.cz
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: x86@kernel.org