drop deprecated KERNEL_UPGRADE_FREEZE feature

Was only used once (orangepi5pro.csc) and has been deprecated.
Remove the implementation, the board config, and the README entry.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

config/boards/README.md

@@ -80,7 +80,6 @@ If you are unsure about the documentation then invoke `$ grep -r -A5 -B5 "BUILD_
 		- [branch]: Use specified [branch] kernel
 		- [none]: Exits with error
 - **KERNEL_TEST_TARGET** ( comma-separated list of kernel releases or branches ): if test targets are different for testings. Also applies to build list generation. (internal switch)
-- **KERNEL_UPGRADE_FREEZE** ( comma-separated list of kernels with versions obove which they stop updating, example: KERNEL_UPGRADE_FREEZE="vendor-rk35xx@24.8.1,current-rockchip-rk3588@24.8.2" )
 - **FULL_DESKTOP** ( boolean ): defines whether to install desktop stack of applications such as office, thunderbird, etc..
 	- Values:
 		- yes: install desktop stack

config/boards/orangepi5pro.csc

@@ -14,7 +14,6 @@ BOOT_SCENARIO="spl-blobs"
 BOOT_SUPPORT_SPI="yes"
 BOOT_SPI_RKSPI_LOADER="yes"
 IMAGE_PARTITION_TABLE="gpt"
-KERNEL_UPGRADE_FREEZE="vendor-rk35xx@24.8.1"
 
 function post_family_tweaks__orangepi5pro_naming_audios() {
 	display_alert "$BOARD" "Renaming orangepi5pro audios" "info"

lib/functions/bsp/armbian-bsp-cli-deb.sh

@@ -229,23 +229,6 @@ function compile_armbian-bsp-cli() {
 	artifact_package_hook_helper_board_side_functions "postinst" board_side_bsp_cli_postinst_base "${postinst_functions[@]}" board_side_bsp_cli_postinst_finish
 	unset board_side_bsp_cli_postinst_base board_side_bsp_cli_postinst_update_uboot_bootscript board_side_bsp_cli_postinst_finish
 
-	### preventing upgrading stable kernels beyond version if defined
-	# if freeze variable is removed, upgrade becomes possible again
-	if [[ "${BETA}" != "yes" ]]; then
-		for pin_variants in $(echo $KERNEL_UPGRADE_FREEZE | sed "s/,/ /g"); do
-			IFS=' ' read -ra extracted_pins <<< "${pin_variants//@/ }"
-			if [[ "${BRANCH}-${LINUXFAMILY}" == "${extracted_pins[0]}" ]]; then
-				cat <<- EOF >> "${destination}"/etc/apt/preferences.d/frozen-armbian
-					Package: linux-*-${extracted_pins[0]}
-					Pin: version ${extracted_pins[1]}
-					Pin-Priority: 999
-				EOF
-			fi
-		done
-	else
-		touch "${destination}"/etc/apt/preferences.d/frozen-armbian
-	fi
-
 	# add some summary to the image # @TODO: another?
 	fingerprint_image "${destination}/etc/armbian.txt"