iwlwifi: mvm: disable scheduled scan

The iwlwifi scheduled scan implementation doesn't adhere to the
userspace API correctly - the API assumes that any new incoming
'incompatible' request (like scan or remain-on-channel for this
driver) will just cancel the scheduled scan. Instead our driver
relies on userspace cancelling it, thus breaking existing wpa_s
versions.

Cc: stable@vger.kernel.org [3.13]
Fixes: 35a000b7 ("iwlwifi: mvm: support sched scan if supported by the fw")
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>