lib/systems: remove unused platforms

These were not used by the selection logic or
`lib/systems/examples.nix`, so any consumer would have to be including
them explicitly. Since we’re moving away from setting Linux kernel
configuration in the platform structure, breaking these explictily
won’t reduce the convenience and will help signal to any such expert
users that they need to move their kernel configuration elsewhere.

lib/systems/platforms.nix

@@ -226,31 +226,6 @@ rec {
     };
   };
 
-  utilite = {
-    linux-kernel = {
-      name = "utilite";
-      maseConfig = "multi_v7_defconfig";
-      autoModules = false;
-      extraConfig = ''
-        # Ubi for the mtd
-        MTD_UBI y
-        UBIFS_FS y
-        UBIFS_FS_XATTR y
-        UBIFS_FS_ADVANCED_COMPR y
-        UBIFS_FS_LZO y
-        UBIFS_FS_ZLIB y
-        UBIFS_FS_DEBUG n
-      '';
-      makeFlags = [ "LOADADDR=0x10800000" ];
-      target = "uImage";
-      DTB = true;
-    };
-    gcc = {
-      cpu = "cortex-a9";
-      fpu = "neon";
-    };
-  };
-
   # https://developer.android.com/ndk/guides/abis#v7a
   armv7a-android = {
     linux-kernel.name = "armeabi-v7a";
@@ -379,35 +354,6 @@ rec {
     };
   };
 
-  # based on:
-  #   https://www.mail-archive.com/qemu-discuss@nongnu.org/msg05179.html
-  #   https://gmplib.org/~tege/qemu.html#mips64-debian
-  mips64el-qemu-linux-gnuabi64 = {
-    linux-kernel = {
-      name = "mips64el";
-      baseConfig = "64r2el_defconfig";
-      target = "vmlinuz";
-      autoModules = false;
-      DTB = true;
-      # for qemu 9p passthrough filesystem
-      extraConfig = ''
-        MIPS_MALTA y
-        PAGE_SIZE_4KB y
-        CPU_LITTLE_ENDIAN y
-        CPU_MIPS64_R2 y
-        64BIT y
-        CPU_MIPS64_R2 y
-
-        NET_9P y
-        NET_9P_VIRTIO y
-        9P_FS y
-        9P_FS_POSIX_ACL y
-        PCI y
-        VIRTIO_PCI y
-      '';
-    };
-  };
-
   ##
   ## Other
   ##