thinkpad_acpi: Remember adaptive kbd presence

Rather than checking on each suspend and resume whether the laptop
has an adaptive keyboard, check when the driver is initialised.

Signed-off-by: Bastien Nocera <hadess@hadess.net>
Acked-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
Signed-off-by: Darren Hart <dvhart@linux.intel.com>