bootconfig: Fix to prevent warning message if no bootconfig option

Commit de462e5f ("bootconfig: Fix to remove bootconfig
data from initrd while boot") causes a cosmetic regression
on dmesg, which warns "no bootconfig data" message without
bootconfig cmdline option.

Fix setup_boot_config() by moving no bootconfig check after
commandline option check.

Link: http://lkml.kernel.org/r/9b1ba335-071d-c983-89a4-2677b522dcc8@molgen.mpg.de
Link: http://lkml.kernel.org/r/158916116468.21787.14558782332170588206.stgit@devnote2

Fixes: de462e5f

 ("bootconfig: Fix to remove bootconfig data from initrd while boot")
Reported-by: Paul Menzel <pmenzel@molgen.mpg.de>
Reviewed-by: Paul Menzel <pmenzel@molgen.mpg.de>
Signed-off-by: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>