wil6210: update cid boundary check of wil_find_cid/_by_idx()

The return value of wil_find_cid()/wil_find_cid_by_idx() is
validated with the lower boundary value.
Check the upper boundary value as well.

Signed-off-by: Alexei Avshalom Lazar <ailizaro@codeaurora.org>
Signed-off-by: Maya Erez <merez@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>