wifi: wcn36xx: fix channel survey memory allocation size

In the Linux kernel, the following vulnerability has been resolved: 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.