[WIRELESS]: Update MAINTAINERS for wireless mailing list.

This patch adds the linux-wireless mailing list to all appropriate
entries in the MAINTAINERS file.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>