hp-wmi: acpi_drivers.h is already included through acpi.h two lines below

Signed-off-by: Thomas Renninger <trenn@suse.de>
CC: linux-acpi@vger.kernel.or
CC: platform-driver-x86@vger.kernel.org
CC: mjg@redhat.com
Signed-off-by: Matthew Garrett <mjg@redhat.com>