systemconfig: /boot needs to go inside /persist

interestingly, we only see this when it boots from mmc, because
for tftpboot the bootloader has already performed negotiation
and therefore it works despite the missing option.

devices/turris-omnia/default.nix

@@ -130,6 +130,7 @@
             MVNETA_BM_ENABLE = "y";
             SRAM = "y"; # mmio-sram is "compatible" for bm_bppi reqd by BM
             PHY_MVEBU_A38X_COMPHY = "y"; # for eth2
+            MARVELL_PHY = "y";
 
             MVPP2 = "y";
             MV_XOR = "y";

pkgs/systemconfig/default.nix

@@ -95,7 +95,7 @@ in attrset:
       if test -d $dest/persist; then dest=$dest/persist; fi
       cp -v -fP \$src/bin/* \$src/etc/* \$dest
       ${if attrset ? boot then ''
-        (cd \$prefix && rm ./boot && ln -sf ${lib.strings.removePrefix "/" attrset.boot.target} ./boot)
+        (cd \$dest && rm ./boot && ln -sf ${lib.strings.removePrefix "/" attrset.boot.target} ./boot)
       '' else ""}
       EOF
       chmod +x $out/bin/install