wil6210: add 'freq' and 'link' debugfs entries

Expose operational frequency and link info

Change-Id: Iacd7689faeb1d02c4e533ad99996a770d207c0f9
Signed-off-by: Vladimir Kondratiev <qca_vkondrat@qca.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Git-commit: 9eb82d43da0618f6bab78de0f18e7405085dd955
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/linville/wireless-testing.git


[hkadmany@codeaurora.org: trivial backport to kernel 3.10]
Signed-off-by: Hamad Kadmany <hkadmany@codeaurora.org>