staging: delete rtl8187se wireless driver

There is a "real" driver for this hardware now in drivers/net/ so remove
the staging version as it's not needed anymore.

Reported-by: Xose Vazquez Perez <xose.vazquez@gmail.com>
Cc: Larry Finger <Larry.Finger@lwfinger.net>
Cc: John W. Linville" <linville@tuxdriver.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>