platform/x86: hp-wmi: Fix error value for hp_wmi_tablet_state

hp_wmi_tablet_state() fails to return the correct error code when
hp_wmi_perform_query() returns the HP WMI query specific error code
that is a positive value.

Signed-off-by: Carlo Caione <carlo@endlessm.com>
Signed-off-by: Darren Hart (VMware) <dvhart@infradead.org>