fujitsu-laptop: Clear build warnings

When CONFIG_FUJITSU_LAPTOP_DEBUG is disabled and W=1, the
fujitsu-laptop driver builds with the following warnings:

drivers/platform/x86/fujitsu-laptop.c: In function "bl_update_status":
drivers/platform/x86/fujitsu-laptop.c:409:8: warning: suggest braces around empty body in an "if" statement [-Wempty-body]
    ret);
        ^
drivers/platform/x86/fujitsu-laptop.c:418:8: warning: suggest braces around empty body in an "if" statement [-Wempty-body]
    ret);
        ^

Rework the debug printk helper macro to get rid of these. I verified
that this change has no effect on the generated binary, both in the
debug and non-debug case.

Signed-off-by: Jean Delvare <jdelvare@suse.de>
Acked-by: Jonathan Woithe <jwoithe@just42.net>
Cc: Matthew Garrett <matthew.garrett@nebula.com>
Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>