[PATCH] net/: fix the WIRELESS_EXT abuse

This patch contains the following changes:
- add a CONFIG_WIRELESS_EXT select'ed by NET_RADIO for conditional
  code
- remove the now no longer required #ifdef CONFIG_NET_RADIO from some
  #include's

Based on a patch by Jean Tourrilhes <jt@hpl.hp.com>.

Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>