wifi: wilc1000: remove WEP security support

Deprecated WEP security for WILC driver as well as in firmware from
15.6 FW release onwards. After WEP security removal, freeup some codespace
which helped to add new features like WPA3 etc.

Signed-off-by: Ajay Singh <ajay.kathat@microchip.com>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20220524120606.9675-2-ajay.kathat@microchip.com