platform/kevin: factor out modules_{no}insmod as a let-block

src/platform/kevin/default.nix

@@ -1,30 +1,4 @@
-{
+let
-  hostPlatform = (import <nixpkgs/lib>).systems.examples.aarch64-multiplatform;
-
-  overlay = (final: prev: {
-    nixpkgsOnBuildForHost = prev.nixpkgsOnBuildForBuild.pkgsCross.aarch64-multiplatform;
-
-    platform_name = "kevin";
-
-    kernel =
-      let version = "5.10.10"; in
-      final.lib.makeOverridable (prev.kernel.override {
-        config = ./linux.config;
-        buildTargets = [ "Image" "dtbs" ];
-      }).overrideAttrs (a: {
-        inherit version;
-        src = final.nixpkgsOnBuildForBuild.fetchurl {
-          url = "mirror://kernel/linux/kernel/v5.x/linux-${version}.tar.xz";
-          sha256 = "sha256-YO2Gb6lRUipSVeo37DrCAG0/NCfUeDoT70eEZPN82xk=";
-          # FIXME: add the patches
-        };
-        postInstall = (a.postInstall or "") + ''
-          lzma < arch/arm64/boot/Image > $out/Image.lzma
-          cp arch/arm64/boot/dts/rockchip/rk3399-gru-kevin.dtb $out/
-        '';
-      });
-
-    userspace = prev.userspace.override {
   # order matters!  this is also the order in which the modules are insmoded
   modules_insmod = [
     "drivers/video/backlight/pwm_bl.ko"
@@ -56,6 +30,35 @@
     "drivers/net/wireless/marvell/mwifiex/mwifiex_pcie.ko"
     "drivers/net/wireless/marvell/mwifiex/mwifiex.ko"
   ];
+in {
+  hostPlatform = (import <nixpkgs/lib>).systems.examples.aarch64-multiplatform;
+
+  overlay = (final: prev: {
+    nixpkgsOnBuildForHost = prev.nixpkgsOnBuildForBuild.pkgsCross.aarch64-multiplatform;
+
+    platform_name = "kevin";
+
+    kernel =
+      let version = "5.10.10"; in
+      final.lib.makeOverridable (prev.kernel.override {
+        config = ./linux.config;
+        buildTargets = [ "Image" "dtbs" ];
+      }).overrideAttrs (a: {
+        inherit version;
+        src = final.nixpkgsOnBuildForBuild.fetchurl {
+          url = "mirror://kernel/linux/kernel/v5.x/linux-${version}.tar.xz";
+          sha256 = "sha256-YO2Gb6lRUipSVeo37DrCAG0/NCfUeDoT70eEZPN82xk=";
+          # FIXME: add the patches
+        };
+        postInstall = (a.postInstall or "") + ''
+          lzma < arch/arm64/boot/Image > $out/Image.lzma
+          cp arch/arm64/boot/dts/rockchip/rk3399-gru-kevin.dtb $out/
+        '';
+      });
+
+    userspace = prev.userspace.override {
+      inherit modules_insmod;
+      inherit modules_noinsmod;
     };
 
     coreboot =