ec/lenovo/h8/acpi: Replace Subtract(a,b,c) with ASL 2.0 syntax

Replace `Subtract (a, b, c)` with `c = a - b`.

Change-Id: Ic38c60503fedaffc66153e103d40fda86781f9c8
Signed-off-by: Felix Singer <felixsinger@posteo.net>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/60478
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: HAOUAS Elyes <ehaouas@noos.fr>

src/ec/lenovo/h8/acpi/thermal.asl

@@ -85,11 +85,11 @@ External (\PPKG, MethodObj)
 			Store (GPSV (), Local0)
 
 			/* Active fan 10 degree below passive threshold */
-			Subtract (Local0, 10, Local0)
+			Local0 -= 10
 
 			If (\FLVL) {
 				/* Turn of 5 degree below trip point */
-				Subtract (Local0, 5, Local0)
+				Local0 -= 5
 			}
 
 			Return (C2K (Local0))