udev hwdb: Change error message regarding missing hwdb.bin back to debug.

When used in an initramfs, it's expected that the hwdb.bin file is
not present (it makes for a very large initramfs otherwise).

While it's nice to tell the user about this, as it's not strictly
speaking an error we really shouldn't be so forceful in our
reporting.

src/libudev/libudev-hwdb.c

@@ -296,7 +296,7 @@ _public_ struct udev_hwdb *udev_hwdb_new(struct udev *udev) {
         }
 
         if (!hwdb->f) {
-                udev_err(udev, "hwdb.bin does not exist, please run udevadm hwdb --update");
+                udev_dbg(udev, "hwdb.bin does not exist, please run udevadm hwdb --update");
                 udev_hwdb_unref(hwdb);
                 return NULL;
         }