fix dropbear startup, add mips64 qemu bug notice

BUGS

@@ -1,2 +1,3 @@
 - openssh on amd64 does not work, ssh-keygen endless loop
 - uclibc on lemote mips64 target does not work (only uclibc-trunk with patches)
+- qemu-mips64* targets does not boot, kernel problem?

package/dropbear/files/dropbear.postinst

@@ -1,3 +1,3 @@
 #!/bin/sh
 . $IPKG_INSTROOT/etc/functions.sh
-add_rcconf '"NO" to disable' dropbear_flags ""
+add_rcconf '"NO" to disable' dropbear_flags " "