staging: wilc1000: rename pu8WepKey of struct host_if_wep_attr

This patch renames pu8WepKey of struct host_if_wep_attr to key in order
to avoid CamelCase naming convention.

Signed-off-by: Tony Cho <tony.cho@atmel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>