Add AM antenna attenuation

src/constants.h

@@ -101,9 +101,9 @@
 
 // EEPROM index defines
 #define EE_PRESETS_CNT              30
-#define EE_CHECKBYTE_VALUE          16 // 0 ~ 255,add new entry, change for new value 
+#define EE_CHECKBYTE_VALUE          18 // 0 ~ 255,add new entry, change for new value 
 
-#define EE_TOTAL_CNT                276
+#define EE_TOTAL_CNT                277
 #define EE_UINT16_FREQUENCY_FM      0
 #define EE_BYTE_VOLSET              4
 #define EE_BYTE_STEREO              5
@@ -174,6 +174,7 @@
 #define EE_BYTE_BATTERY_OPTIONS     273
 #define EE_BYTE_AM_CO_DECT          274
 #define EE_BYTE_AM_CO_DECT_COUNT    275
+#define EE_BYTE_AM_RF_AGC           276
 // End of EEPROM index defines
 
 static const char* const unitString[] = {"dBμV", "dBf", "dBm"};