sdk: remove redundant symbol declaration

Commit d79f8909 introduced CONFIG_ALL,
CONFIG_ALL_KMODS and CONFIG_ALL_NONSHARED as menuconfig choices to the SDK,
therefor we can drop the hardcoded CONFIG_ALL symbol declaration now.

Signed-off-by: Jo-Philipp Wich <jo@mein.io>

target/sdk/convert-config.pl

 #!/usr/bin/env perl
 use strict;
 
-print <<EOF;
-config ALL
-	bool
-	default y
-
-EOF
-
 while (<>) {
 	chomp;
 	next if /^CONFIG_SIGNED_PACKAGES/;