[orion]: don't copy the zImages to the bin dir, factory u-boots can't use them

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@36850 3c298f89-4303-0410-b956-a3cf2f4a3e73
[orion]: only copy uImages to the bin dir on ramdisk builds

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@36851 3c298f89-4303-0410-b956-a3cf2f4a3e73