staging: wilc1000: rename pRemainOnChanExpired of struct remain_ch

This patch renames pRemainOnChanExpired of struct remain_ch to expired
to avoid CamelCase naming convention.

Signed-off-by: Leo Kim <leo.kim@atmel.com>
Signed-off-by: Glen Lee <glen.lee@atmel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>