staging: wilc1000: rename P2P_LISTEN_STATE variable to use lowercase

Rename P2P_LISTEN_STATE variable to avoid using uppercase for variable
name to follow linux coding style.

Signed-off-by: Ajay Singh <ajay.kathat@microchip.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>