linux_5_7: init at 5.7.1

Changes:
- Copied linux-5.7.nix from linux-5.6.nix
- Add linux_5_7 and linuxPackages_5_7
- Update linux_latest to 5.7

Note:
The kernel patch 'kernelPatches.export_kernel_fpu_functions."5.3"' is
still applied as I copied the list from linux_5_7 (vs. linux_testing).
This patch is probably still required for the ZFS performance.

(cherry picked from commit 19b2efb)

pkgs/os-specific/linux/kernel/linux-5.7.nix

@@ -0,0 +1,18 @@
+{ stdenv, buildPackages, fetchurl, perl, buildLinux, modDirVersionArg ? null, ... } @ args:
+
+with stdenv.lib;
+
+buildLinux (args // rec {
+  version = "5.7.1";
+
+  # modDirVersion needs to be x.y.z, will automatically add .0 if needed
+  modDirVersion = if (modDirVersionArg == null) then concatStringsSep "." (take 3 (splitVersion "${version}.0")) else modDirVersionArg;
+
+  # branchVersion needs to be x.y
+  extraMeta.branch = versions.majorMinor version;
+
+  src = fetchurl {
+    url = "mirror://kernel/linux/kernel/v5.x/linux-${version}.tar.xz";
+    sha256 = "1vcxrrb2i4366iciw0mfahwbdrzmhrrsr7gi4vdkzznfv2niils0";
+  };
+} // (args.argsOverride or {}))

pkgs/top-level/all-packages.nix

@@ -16540,6 +16540,14 @@ in
     ];
   };
 
+  linux_5_7 = callPackage ../os-specific/linux/kernel/linux-5.7.nix {
+    kernelPatches = [
+      kernelPatches.bridge_stp_helper
+      kernelPatches.request_key_helper
+      kernelPatches.export_kernel_fpu_functions."5.3"
+    ];
+  };
+
   linux_testing = callPackage ../os-specific/linux/kernel/linux-testing.nix {
     kernelPatches = [
       kernelPatches.bridge_stp_helper
@@ -16747,7 +16755,7 @@ in
   linux = linuxPackages.kernel;
 
   # Update this when adding the newest kernel major version!
-  linuxPackages_latest = linuxPackages_5_6;
+  linuxPackages_latest = linuxPackages_5_7;
   linux_latest = linuxPackages_latest.kernel;
 
   # Build the kernel modules for the some of the kernels.
@@ -16762,6 +16770,7 @@ in
   linuxPackages_4_19 = recurseIntoAttrs (linuxPackagesFor pkgs.linux_4_19);
   linuxPackages_5_4 = recurseIntoAttrs (linuxPackagesFor pkgs.linux_5_4);
   linuxPackages_5_6 = recurseIntoAttrs (linuxPackagesFor pkgs.linux_5_6);
+  linuxPackages_5_7 = recurseIntoAttrs (linuxPackagesFor pkgs.linux_5_7);
 
   # Kernels removed on release-20.03
   linuxPackages_5_5 = throw ''