[PATCH] softmac: return -EAGAIN from getscan while scanning

Below patch was developed after discussion with Daniel Drake who
mentioned to me that wireless tools expect an EAGAIN return from getscan
so that they can wait for the scan to finish before printing out the
results.

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