wifi: iwlwifi: mvm: fix 6 GHz scan construction

In the Linux kernel, the following vulnerability has been resolved: wifi: iwlwifi: mvm: fix 6 GHz scan construction If more than 255 colocated APs exist for the set of all APs found during 2.4/5 GHz scanning, then the 6 GHz scan construction will loop forever since the loop variable has type u8, which can never reach the number found when that's bigger than 255, and is stored in a u32 variable. Also move it into the loops to have a smaller scope. Using a u32 there is fine, we limit the number of APs in the scan list and each has a limit on the number of RNR entries due to the frame size. With a limit of 1000 scan results, a frame size upper bound of 4096 (really it's more like ~2300) and a TBTT entry size of at least 11, we get an upper bound for the number of ~372k, well in the bounds of a u32.