kernel: fix EDID firmware loading

for context:
- https://github.com/NixOS/nixpkgs/pull/279789#discussion_r1624936659
- https://github.com/NixOS/nixpkgs/pull/279789#issuecomment-2148560802
- https://github.com/NixOS/nixpkgs/pull/279789#issuecomment-2150726766

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

@@ -1147,6 +1147,8 @@ let
       # For systemd-binfmt
       BINFMT_MISC   = option yes;
 
+      # Required for EDID overriding
+      FW_LOADER = yes;
       # Disable the firmware helper fallback, udev doesn't implement it any more
       FW_LOADER_USER_HELPER_FALLBACK = option no;
 

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

@@ -219,7 +219,7 @@ let
 
     config = {
       CONFIG_MODULES = "y";
-      CONFIG_FW_LOADER = "m";
+      CONFIG_FW_LOADER = "y";
       CONFIG_RUST = if withRust then "y" else "n";
     };
   });