brcm47xx: extend firmware validation

This provides TRX validation result, so final JSON may look like:
{
	"tests": {
		"fwtool_signature": true,
		"fwtool_device_match": true,
		"trx_valid": true
	},
	"valid": true,
	"forceable": true
}

It also prevents users from installing broken firmware files, e.g.:

root@OpenWrt:/# sysupgrade -F -n /tmp/TZ
Image metadata not found
Invalid image type. Please use firmware specific for this device.
Image check failed but --force given - will update anyway!
Commencing upgrade. Closing all shell sessions.
Firmware image is broken and cannot be installed

Signed-off-by: Rafał Miłecki <rafal@milecki.pl>
(cherry picked from commit e68c1cebd1d87ce60f0646688e437e83081e2322)

target/linux/brcm47xx/base-files/lib/upgrade/platform.sh

@@ -98,7 +98,10 @@ platform_check_image() {
 
 			if ! otrx check "$1" -o "$header_len"; then
 				echo "No valid TRX firmware in the CHK image"
+				notify_firmware_test_result "trx_valid" 0
 				error=1
+			else
+				notify_firmware_test_result "trx_valid" 1
 			fi
 		;;
 		"cybertan")
@@ -113,17 +116,24 @@ platform_check_image() {
 
 			if ! otrx check "$1" -o 32; then
 				echo "No valid TRX firmware in the CyberTAN image"
+				notify_firmware_test_result "trx_valid" 0
 				error=1
+			else
+				notify_firmware_test_result "trx_valid" 1
 			fi
 		;;
 		"trx")
 			if ! otrx check "$1"; then
 				echo "Invalid (corrupted?) TRX firmware"
+				notify_firmware_test_result "trx_valid" 0
 				error=1
+			else
+				notify_firmware_test_result "trx_valid" 1
 			fi
 		;;
 		*)
-			echo "Invalid image type. Please use only .trx files"
+			echo "Invalid image type. Please use firmware specific for this device."
+			notify_firmware_broken
 			error=1
 		;;
 	esac