wifi: wcn36xx: fix channel survey memory allocation size

wifi: wcn36xx: fix channel survey memory allocation size

KASAN reported a memory allocation issue in wcn->chan_survey
due to incorrect size calculation.
This commit uses kcalloc to allocate memory for wcn->chan_survey,
ensuring proper initialization and preventing the use of uninitialized
values when there are no frames on the channel.

Fixes: 29696e0aa413 ("wcn36xx: Track SNR and RSSI for each RX frame")
Signed-off-by: Barnabás Czémán <barnabas.czeman@mainlining.org>
Acked-by: Loic Poulain <loic.poulain@linaro.org>
Reviewed-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Link: https://patch.msgid.link/20241104-wcn36xx-memory-allocation-v1-1-5ec901cf37b6@mainlining.org
Signed-off-by: Jeff Johnson <quic_jjohnson@quicinc.com>