linux/common-config: enable EFI on supported platforms (#406320)

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

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         DVB_DYNAMIC_MINORS = option yes; # we use udev
 
+        EFI = lib.mkIf stdenv.hostPlatform.isEfi yes;
         EFI_STUB = yes; # EFI bootloader in the bzImage itself
         EFI_GENERIC_STUB_INITRD_CMDLINE_LOADER = whenOlder "6.2" (whenAtLeast "5.8" yes); # initrd kernel parameter for EFI