config: Fix type for devicetree setting

Author: DaanDeMeyer

mkosi/config.py

@@ -2014,7 +2014,7 @@ class Config:
     initrd_packages: list[str]
     initrd_volatile_packages: list[str]
     microcode_host: bool
-    devicetree: Optional[Path]
+    devicetree: Optional[str]
     splash: Optional[Path]
     kernel_command_line: list[str]
     kernel_modules_include: list[str]

tests/test_json.py

@@ -510,7 +510,7 @@ def test_config() -> None:
         make_initrd=False,
         manifest_format=[ManifestFormat.json, ManifestFormat.changelog],
         microcode_host=True,
-        devicetree=Path("freescale/imx8mm-verdin-nonwifi-dev.dtb"),
+        devicetree="freescale/imx8mm-verdin-nonwifi-dev.dtb",
         minimum_version="123",
         mirror=None,
         nspawn_settings=None,