Remove unconfigurable cts_protection_type

This was included in the AP configuration parameters, but there has
been no way to set it to anything else than the default automatic
mode. Remove this parameter and just hardcode ERP determination to
follow the automatic mode.

src/ap/ap_config.h

@@ -381,12 +381,6 @@ struct hostapd_config {
 		LONG_PREAMBLE = 0,
 		SHORT_PREAMBLE = 1
 	} preamble;
-	enum {
-		CTS_PROTECTION_AUTOMATIC = 0,
-		CTS_PROTECTION_FORCE_ENABLED = 1,
-		CTS_PROTECTION_FORCE_DISABLED = 2,
-		CTS_PROTECTION_AUTOMATIC_NO_OLBC = 3,
-	} cts_protection_type;
 
 	int *supported_rates;
 	int *basic_rates;