staging: wilc1000: don't use wdev while setting tx power

WILC doesn't support per-vif tx power, and hence, wdev will always be
null in calls to set_tx_power.
Instead, wiphy should be used to execute the operation

Signed-off-by: Adham Abozaeid <adham.abozaeid@microchip.com>
Link: https://lore.kernel.org/r/20191004214011.7623-1-adham.abozaeid@microchip.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>