setup non-free and contrib repo by default

Signed-off-by: Robert Nelson <robertcnelson@gmail.com>

scripts/squeeze-preseed.cfg

@@ -1,3 +1,8 @@
+### Apt setup
+# You can choose to install non-free and contrib software.
+d-i apt-setup/non-free boolean true
+d-i apt-setup/contrib boolean true
+
 # Individual additional packages to install
 d-i pkgsel/include string uboot-mkimage pastebinit initramfs-tools wget firmware-linux ntpdate