cfg80211: add checks for beacon rate, extend to mesh

The previous commit added support for specifying the beacon rate
for AP mode. Add features checks to this, and extend it to also
support the rate configuration for mesh networks. For IBSS it's
not as simple due to joining etc., so that's not yet supported.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>

Git-commit: 8564e38206de2ff005a27c8d7c2ce3869a44f0dd
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/jberg/mac80211-next.git


Change-Id: Id1f43276701f805dc93d2bcdabec4f333942e31c
CRs-fixed: 1096202
[pkushwah@codeaurora.org: an additional check for NULL chan in chandef is
added before the validation.
backport to 3.18-This commit includes the changes from following commits
in include/uapi/linux/nl80211.h to compile for msm-3.18.
ffc1199122d83d60ad99f9c55df32feb650b7bff :
cfg80211: add VHT support for IBSS
0c9ca11b1ae8eb16c1b6bbae91991392d2321372 :
cfg80211: Add global RRM capability
c6e6a0c8be575c830a97b1942dabeab70f423fe0 :
nl80211: Add API to support VHT MU-MIMO air sniffer
1d76250bd34af86c6498fc51e50cab3bfbbeceaa :
nl80211: support beacon report scanning ]
Signed-off-by: Purushottam Kushwaha <pkushwah@codeaurora.org>