platform/x86: hp-wmi: Fix tablet mode detection for convertibles

Commit f9cf3b28 ("platform/x86: hp-wmi: Refactor dock and tablet
state fetchers") consolidated the methods for docking and laptop mode
detection, but omitted to apply the correct mask for the laptop mode
(it always uses the constant for docking).

Fixes: f9cf3b28

 ("platform/x86: hp-wmi: Refactor dock and tablet state fetchers")
Signed-off-by: Stefan Brüns <stefan.bruens@rwth-aachen.de>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>