Frequency analyzer fixes and improvements

disable ext module due to lack of required hardware on them and incorrect usage of freq analyzer, like trying to receive "signals" with it (from the space??), while it should be used only to get frequency of the remote placed around 1-10cm around flipper's left corner

Also fix possible GSM mobile towers signal interference by limiting upper freq to 920mhz max

Fix dupliacted freq lists and use user config for nearest freq selector too (finally)

documentation/SubGHzSettings.md

@@ -30,6 +30,8 @@ if you need your custom one, make sure it doesn't listed here
     314980000,
     315000000,
     318000000,
+    320000000,
+    320150000,
     330000000,
     345000000,
     348000000,