mwifiex: don't use IEEE80211_MAX_QUEUES

mwifiex: don't use IEEE80211_MAX_QUEUES

IEEE80211_MAX_QUEUES is an internal mac80211 value,
it is not guaranteed to be always 4. The firmware
API in mwifiex almost certainly doesn't care about
mac80211 changing though, so mwifiex shouldn't use
this value.

Maybe it should use IEEE80211_NUM_ACS instead and
that is what I'm doing here as at least that value
will probably never change, but maybe it should
have its own define instead.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Acked-by: Bing Zhao <bzhao@marvell.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>