staging/wilc1000: remove linux_wlan_{device_power,device_detection}

The driver provides an interface for custom power management
and detection that is meant to be filled by people customizing
the driver. The default implementation of this is empty, and
we don't actually want people to have to modify the source code.

If anybody needs this, they need to describe the respective
hardware specifics using device tree or platform data and make
the driver handle this is a more general way.

This removes the empty stubs.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>