mb/roda/rk9/acpi: Replace Add(a,b,c) with ASL 2.0 syntax

Replace `Add (a, b, c)` with `c = a + b`.

Change-Id: If2bb935570b1cb2b7a5e4168d594d735f343369b
Signed-off-by: Felix Singer <felixsinger@posteo.net>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/60487
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: HAOUAS Elyes <ehaouas@noos.fr>

src/mainboard/roda/rk9/acpi/thermal.asl

@@ -6,7 +6,7 @@ Scope (\_TZ)
 {
 	/* degree Celsius to deci-Kelvin (ACPI temperature unit) */
 	Method(C2dK, 1) {
-		Add (2732, Multiply (Arg0, 10), Local0)
+		Local0 = 2732 + Multiply (Arg0, 10)
 		Return (Local0)
 	}