wireless: depends on NET

When CONFIG_NET is disabled, the attempt to build wext-priv.c
fails with:

net/wireless/wext-priv.c: In function 'ioctl_private_call':
net/wireless/wext-priv.c:207: error: implicit declaration of function 'call_commit_handler'

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>