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.

Change-Id: Iadf22f3692783f29dd6e08205ceeb9981bca302c
Signed-off-by: Alexei Avshalom Lazar <ailizaro@codeaurora.org>