tools/bootconfig: Fix to return 0 if succeeded to show the bootconfig

tools/bootconfig: Fix to return 0 if succeeded to show the bootconfig

Fix bootconfig to return 0 if succeeded to show the bootconfig
in initrd. Without this fix, "bootconfig INITRD" command
returns !0 even if the command succeeded to show the bootconfig.

Link: http://lkml.kernel.org/r/159230246566.65555.11891772258543514487.stgit@devnote2
Cc: stable@vger.kernel.org
Fixes: 5840f552600b ("tools: bootconfig: Add bootconfig command")
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>