Patch from Pavel Machek

Also warn users about charging in unsuitable temperature.
Signed-off-by: Pavel Machek <pavel@suse.cz>
Acked-by: Richard Purdie <rpurdie@rpsys.net>
Acked-by: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>