firmware: Promote the latest beta firmware to stable

The beta release with supports network boot is now stable enough
for most configurations. This is now frozen except for major bugs
in order to allow more experimental features to be released as
beta.

firmware/release-notes.md

@@ -1,5 +1,16 @@
 # Raspberry Pi4 bootloader EEPROM release notes
 
+## 2020-02-27 rpi-eeprom-update & firmware
+    * Remove the dependency check for the vl805 utility. This is deprecated
+      and there is no 64-bit version. The file is still available in Github
+      for anyone who wants to continue using USE_FLASHROM or create their
+      own scripts.
+    * Add a stable firmware directory based on the latest beta release.
+      Stable should be interpreted as feature-freeze releases. In this
+      case the core network boot is stable enough for most scenarios
+      and this de-risks adding new more experimental features in the
+      beta folder.
+
 ## 2020-01-22 - vl805 00137ad
     * Set the default/critical vl805 version to be 00137ad. This has the 
       same power savings as 0137ab but with fixes for USB webcams.