sdk: filter out CONFIG_SIGNED_PACKAGES for generated config

Signed-off-by: Felix Fietkau <nbd@openwrt.org>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@45581 3c298f89-4303-0410-b956-a3cf2f4a3e73

target/sdk/convert-config.pl

@@ -10,6 +10,7 @@ EOF
 
 while (<>) {
 	chomp;
+	next if /^CONFIG_SIGNED_PACKAGES/;
 	next unless /^CONFIG_([^=]+)=(.*)$/;
 
 	my $var = $1;