Proto change for new RSSI poll metric

Adds a new field to store the network frequency for rssi poll
histograms.

Bug: 79864669
Test: compile, unit test

Change-Id: I4a8032c5cb71af03f1af150fed30ba27231069fa
diff --git a/proto/src/wifi.proto b/proto/src/wifi.proto
index 9ff8e7d..d43b50e 100644
--- a/proto/src/wifi.proto
+++ b/proto/src/wifi.proto
@@ -615,6 +615,9 @@
 
   // Number of RSSI polls with 'rssi'
   optional int32 count = 2;
+
+  // Beacon frequency of the channel in MHz
+  optional int32 frequency = 3;
 }
 
 // Number of occurrences of a specific alert reason value