brcmsmac: deactivate ucode sending probe responses

It is possible to configure the ucode to automatically send the probe
responses to the clients after they send a probe request. At least for
WPS the userspace needs to answer the probe requests and we do not know
a way to say to the ucode to just handle the normal probe requests, so
for now no probe requests should be handled by the ucode.

Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>