iwlwifi: mvm: increase scan timeout to 20 seconds

The 16 seconds timeout we were using turned out to be too short.
Recalculations by system show that the total time in both bands should
be < 18.5 seconds, even in the slowest cases (e.g. DCM P2P with
DTIM=2).  Rounding it up to 20 seconds for a bit more safety.

Fixes: 728e825f81b1 ("iwlwifi: mvm: add a scan timeout for regular scans")
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>

drivers/net/wireless/intel/iwlwifi/mvm/scan.c

@@ -1222,7 +1222,7 @@ static int iwl_mvm_check_running_scans(struct iwl_mvm *mvm, int type)
 	return -EIO;
 }
 
-#define SCAN_TIMEOUT (16 * HZ)
+#define SCAN_TIMEOUT (20 * HZ)
 
 void iwl_mvm_scan_timeout(unsigned long data)
 {