firmware: Remove the beta release folder

Remove the beta release folder and replace with a symlink to the
'latest' release.

Including beta firmware in the APT release causes unecessary churn
and occasionally causes an issue where a user might end up on an
old and unsupported beta release.

Instead, beta releases are will be feature specific and installed
manually via 'rpi-eeprom-config --edit beta-firmware.bin'

i.e. beta releases will be out-of-package custom firmware releases
downloaded from github. The functionality will be merged into
a new latest/stable release or abandoned.

N.B. The old beta releases have been archived to 'old' but are no
longer included in APT.

firmware/beta

@@ -0,0 +1 @@
+latest

firmware/release-notes.md

@@ -1,5 +1,12 @@
 # Raspberry Pi4 bootloader EEPROM release notes
 
+## 2023-08-01 - Remove beta release folder
+   * Remove the beta release folder and provide a symlink to stable
+     for backwards compatibility for anyone who has beta in
+     the defaults file.
+     Future beta releases will be "feature-specific" and on a separate
+     branch / download rather than appearing in the generic APT release.
+
 ## 2023-05-15 - Promote pieeprom-2023-05-11 to STABLE
 
 ## 2023-05-11 - Fix hang in secure-boot init - BETA

rpi-eeprom-update

@@ -465,9 +465,10 @@ is a board revision specific variant e.g. default-c03111. If present then the
 board-revision specific version is used in preference.
 
 Release status:
-Bootloader releases follow a pipeline where images are released to the 'beta'
-directory first. The binaries are then promoted to 'latest' and finally 'default'
-so the 'default' binary is always the most tested release.
+Bootloader releases follow a pipeline where images are released to the 'latest'
+directory first. The binaries are then promoted to 'default' once this
+becomes the recommended minimum version and has been proven over time 
+to be stable.
 
 default:
 The default bootloader image which supports all current models and hardware
@@ -477,11 +478,7 @@ If a critical bug fix is required then the minimum default version number
 causing the bootloader to be automatically updated.
 
 latest:
-Contains the latest features which have undergone testing via the 'beta'
-release. Backwards compatiblity for configuration parameters is maintained
-once a feature is in the latest release directory.
-If the 'latest' release is selected then bootloader is automatically upgraded
-when the rpi-eeprom package is updated.
+Contains new features, bug fixes and performance improvements.
 
 As far as rpi-eeprom-update is concerned FIRMWARE_RELEASE_STATUS is just
 the subdirectory mapping under ${FIRMWARE_ROOT}. Therefore, custom release