ACPI sysfs.c strlen fix

commit 9f132652d94c96476b0b0a8caf0c10e96ab10fa8 upstream.

Current code is ignoring the last character of "enable" and "disable"
in comparisons.

https://bugzilla.kernel.org/show_bug.cgi?id=33732

Signed-off-by: Len Brown <len.brown@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>