x86: move hp-wmi's probe function to .devinit.text

A pointer to hp_wmi_bios_setup is passed to the core via
platform_driver_register and so the function must not disappear when the
.init sections are discarded.  Otherwise (if also having HOTPLUG=y)
unbinding and binding a device to the driver via sysfs will result in an
oops as does a device being registered late.

An alternative to this patch is using platform_driver_probe instead of
platform_driver_register plus removing the pointer to the probe function
from the struct platform_driver.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Cc: Frans Pop <elendil@planet.nl>
Cc: Larry Finger <Larry.Finger@lwfinger.net>
Cc: Len Brown <lenb@kernel.org>
Cc: Helge Deller <deller@gmx.de>
Cc: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Matthew Garrett <mjg@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>