Input: tegra-kbc - enable support for the standard "wakeup-source" property

Though the tegra-kbc driver should/will continue to support the legacy
"nvidia,wakeup-source" property to enable keyboard as the wakeup source,
we need to add support for the new standard property "wakeup-source".

This patch adds support for "wakeup-source" property in addition to the
existing "nvidia,wakeup-source" property.

Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>