X86 platform wmi: Introduce debug param to log all WMI events

To give people easily an idea what could be WMI driven on their system.
Introduces:
wmi.debug=[01]

Tested on an acer:
ACPI: WMI: DEBUG Event INTEGER_TYPE - 65535

Situation where a driver registers for specific event and debug
handler gets overridden and set again if the registering driver gets
unloaded again is untested, but should work.

Signed-off-by: Thomas Renninger <trenn@suse.de>
CC: platform-driver-x86@vger.kernel.org
CC: mjg59@srcf.ucam.org
CC: corentin.chary@gmail.com
Signed-off-by: Carlos Corbacho <carlos@strangeworlds.co.uk>
Signed-off-by: Matthew Garrett <mjg@redhat.com>