mac80211: fix honouring rate flags in low-rate transmit

Transmissions with the IEEE80211_TX_CTL_NO_CCK_RATE flag set
(which can come from userspace) were no longer guaranteed to
be transmitted with allowed rates since commit 2103dec1
("mac80211: select and adjust bitrates according to channel
mode") due to a missing rate_flags check in that commit. The
commit also introduced the need to check the 5/10 MHz flags
but accidentally didn't. Fix it by adding the missing check.

Signed-off-by: Andrei Otcheretianski <andrei.otcheretianski@intel.com>
Reviewed-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>