mb/google/slippy: Replace Multiply(a,b,c) with ASL 2.0 syntax

Replace `Multiply (a, b, c)` with `c = a * b`.

Change-Id: I63b8b8a086e2c5ede765855b3c803206edf87690
Signed-off-by: Felix Singer <felixsinger@posteo.net>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/60653
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Sean Rhodes <sean@starlabs.systems>

src/mainboard/google/slippy/acpi/thermal.asl

@@ -35,7 +35,7 @@ Scope (\_TZ)
 		// Convert from Degrees C to 1/10 Kelvin for ACPI
 		Method (CTOK, 1) {
 			// 10th of Degrees C
-			Multiply (Arg0, 10, Local0)
+			Local0 = Arg0 * 10
 
 			// Convert to Kelvin
 			Local0 += 2732
@@ -90,7 +90,7 @@ Scope (\_TZ)
 			Local0 += \_SB.PCI0.LPCB.EC0.TOFS
 
 			// Convert to 1/10 Kelvin
-			Multiply (Local0, 10, Local0)
+			Local0 *= 10
 			Return (Local0)
 		}