ARM: tegra: acer-a500: Use verbose variant of atmel,wakeup-method value

The verbose variant of the atmel,wakeup-method value was lost when patch
that added the property was merged because it conflicted with other patch,
re-add it for consistency.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Thierry Reding <treding@nvidia.com>