mb/google/rex/variants/ovis: Enable EC in device tree

BUG=b:274421383
TEST=util/abuild/abuild -p none -t google/rex -x -a -b ovis

Change-Id: I6f3fa6543a4cec8c2562196105f17fbc7831bab7
Signed-off-by: Jakub Czapiga <jacz@semihalf.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/75577
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Kapil Porwal <kapilporwal@google.com>
Reviewed-by: Eric Lai <eric_lai@quanta.corp-partner.google.com>

src/mainboard/google/rex/variants/ovis/overridetree.cb

@@ -43,5 +43,10 @@ chip soc/intel/meteorlake
 				device i2c 50 on end
 			end
 		end
+		device ref soc_espi on
+			chip ec/google/chromeec
+				device pnp 0c09.0 on end
+			end
+		end
 	end
 end