linux: Adjust config to allow booting of installer ISO on ppc64 (#486572)

pkgs/os-specific/linux/kernel/common-config.nix

@@ -796,6 +796,10 @@ let
       DEVTMPFS = yes;
 
       UNICODE = yes; # Casefolding support for filesystems
+    }
+    // lib.optionalAttrs stdenv.hostPlatform.isPower {
+      # Needed to use the installation iso image formatted for tbxi booting (ISO9660 w/ hybrid HFS+ partition).
+      HFSPLUS_FS = yes;
     };
 
     security = {
@@ -1623,6 +1627,12 @@ let
         # > round to working out why.  The workaround is to build it in[…].
         # > (It won't do any harm on non-Mac systems.)
         I2C_POWERMAC = yes;
+      }
+      // lib.optionalAttrs stdenv.hostPlatform.isPower {
+        # Needed for booting PowerMacs from disc
+        # (the only nice way that doesn't involve messing around with internal drives or in Open Firmware)
+        ATA = yes;
+        PATA_MACIO = yes;
       };
 
     accel = {