Zigbee add EZSP 6.7.8 as Release Candidate firmware

tools/fw_SonoffZigbeeBridge_ezsp/readme.txt

@@ -3,8 +3,7 @@
 ## EmberZNet NCP UART EZSP firmware signed for Sonoff ZBBridge
 
 - `ncp-uart-sw_6.7.6_115200.ota` - recommended stable version for EZSP v6, EZSP v7, and EZSP v8 compatible hosts.
-- `ncp-uart-sw-6.8.0.1_115200.ota` - latest cutting-edge version. largely untested and only for experimentation with EZSP v8 compatible hosts.
-- `ncp-uart-sw_6.5.5_115200.ota` - legacy version for EZSP v4, EZSP v5, EZSP v6, or EZSP v7 compatible hosts.
+- `ncp-uart-sw_6.7.8_115200.ota` - release candidate, supposedly fixing IKEA battery drain issue.
 
 ## EmberZNet and EZSP Protocol Versions
 
@@ -13,3 +12,7 @@ Silicon Labs do not currently have a consolidated list of changes by EmberZNet S
 The largest change was between EZSP v4 (first added in EmberZNet 4.7.2 SDK) and EZSP v5 that was added in EmberZNet 5.9.0 SDK which requires the Legacy Frame ID 0xFF. The change from EZSP v5 to EZSP v6 was done in EmberZNet 6.0.0 SDK. The change from EZSP v6 to EZSP v7 was in EmberZNet 6.4.0 SDK. EmberZNet 6.7.0 SDK added EZSP v8 (and Secure EZSP Protocol Version 2).
 
 Perhaps more important to know is that EZSP v5, v6 and v7 (EmberZNet 6.6.x.x) use the same framing format, but EmberZNet 6.7.x.x/EZSP v8 introduced new framing format and expanded command id field from 8 bits to 16 bits.
+
+## Archived Versions
+
+- `ncp-uart-sw_6.5.5_115200.ota` - legacy version for EZSP v4, EZSP v5, EZSP v6, or EZSP v7 compatible hosts.