wcn36xx: Fix physical location of beacon filter comment

The comment in the header with respect to beacon filtering makes a
reference to "the structure above" and "the structure below" which would be
informative if the comment appeared in the right place but, it does not.

Fix the comment location so that it a least makes sense w/r/t the physical
location statements.

Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://lore.kernel.org/r/20211214134630.2214840-3-bryan.odonoghue@linaro.org