mac80211: deinline rate_control_rate_init, rate_control_rate_update

mac80211: deinline rate_control_rate_init, rate_control_rate_update

With this .config: http://busybox.net/~vda/kernel_config,
after deinlining these functions have sizes and callsite counts
as follows:

rate_control_rate_init: 554 bytes, 8 calls
rate_control_rate_update: 1596 bytes, 5 calls

Total size reduction: about 11 kbytes.

Signed-off-by: Denys Vlasenko <dvlasenk@redhat.com>
CC: John Linville <linville@tuxdriver.com>
CC: Michal Kazior <michal.kazior@tieto.com>
CC: Johannes Berg <johannes.berg@intel.com>
Cc: linux-wireless@vger.kernel.org
Cc: netdev@vger.kernel.org
CC: linux-kernel@vger.kernel.org
Signed-off-by: Johannes Berg <johannes.berg@intel.com>