wireless: airo_cs build fixes

When WEXT_PRIV is not enabled, airo_cs has build errors.
It needs to include net/iw_handler.h and it should select
WEXT_PRIV, like the airo driver does.

drivers/net/wireless/airo.c:7655: error: unknown field 'num_private' specified in initializer
drivers/net/wireless/airo.c:7655: warning: initialization makes pointer from integer without a cast
drivers/net/wireless/airo.c:7656: error: unknown field 'num_private_args' specified in initializer
drivers/net/wireless/airo.c:7656: warning: excess elements in struct initializer
drivers/net/wireless/airo.c:7656: warning: (near initialization for 'airo_handler_def')
drivers/net/wireless/airo.c:7658: error: unknown field 'private' specified in initializer
drivers/net/wireless/airo.c:7658: warning: initialization makes integer from pointer without a cast
drivers/net/wireless/airo.c:7658: error: initializer element is not computable at load time
drivers/net/wireless/airo.c:7658: error: (near initialization for 'airo_handler_def.num_standard')
drivers/net/wireless/airo.c:7659: error: unknown field 'private_args' specified in initializer
drivers/net/wireless/airo.c:7659: warning: initialization from incompatible pointer type

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