add 'phram' param for tftp boot without flashing

modules/phram.nix

@@ -0,0 +1,29 @@
+{
+  config
+, ...
+}:
+{
+  config = {
+    kernel = {
+      checkedConfig = {
+        MTD = "y";
+        MTD_PHRAM = "y";
+        MTD_CMDLINE_PARTS = "y";
+
+        # one or more of the following is required to get from
+        # VFS: Cannot open root device "1f00" or unknown-block(31,0): error -6
+        # to
+        # VFS: Mounted root (squashfs filesystem) readonly on device 31:0.
+        MTD_OF_PARTS = "y";
+        PARTITION_ADVANCED = "y";
+        MSDOS_PARTITION = "y";
+        EFI_PARTITION = "y";
+        MTD_BLKDEVS = "y";
+        MTD_BLOCK = "y";
+
+        # CONFIG_MTD_MTDRAM=m         c'est quoi?
+      };
+
+    };
+  };
+}