wifi: nl80211: fix bounds checker error in nl80211_parse_sched_scan

In the Linux kernel, the following vulnerability has been resolved: wifi: nl80211: fix bounds checker error in nl80211_parse_sched_scan The channels array in the cfg80211_scan_request has a __counted_by attribute attached to it, which points to the n_channels variable. This attribute is used in bounds checking, and if it is not set before the array is filled, then the bounds sanitizer will issue a warning or a kernel panic if CONFIG_UBSAN_TRAP is set. This patch sets the size of allocated memory as the initial value for n_channels. It is updated with the actual number of added elements after the array is filled.