wil6210: check mid is valid

Check that the mid is valid and that it does not exceed the memory
size allocated to vifs array.

Change-Id: I76adf61a78db468bd3a3232f7311f9c6dd9e674a
Signed-off-by: Ahmad Masri <amasri@codeaurora.org>
Signed-off-by: Maya Erez <merez@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Git-commit: e4a29bdd8f82627d88644971235dc12b70c4150b
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/kvalo/ath.git


[merez@codeaurora.org: trivial merge conflict]
Signed-off-by: Maya Erez <merez@codeaurora.org>