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

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

Change-Id: Ie7fa132623c7834e3d2f1acda032928579819a84
Signed-off-by: Felix Singer <felixsinger@posteo.net>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/60489
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: HAOUAS Elyes <ehaouas@noos.fr>

src/mainboard/google/jecht/variants/guado/include/variant/acpi/thermal.asl

@@ -27,7 +27,7 @@ Scope (\_TZ)
 			Multiply (Arg0, 10, Local0)
 
 			// Convert to Kelvin
-			Add (Local0, 2732, Local0)
+			Local0 += 2732
 
 			Return (Local0)
 		}

src/mainboard/google/jecht/variants/jecht/include/variant/acpi/thermal.asl

@@ -27,7 +27,7 @@ Scope (\_TZ)
 			Multiply (Arg0, 10, Local0)
 
 			// Convert to Kelvin
-			Add (Local0, 2732, Local0)
+			Local0 += 2732
 
 			Return (Local0)
 		}

src/mainboard/google/jecht/variants/rikku/include/variant/acpi/thermal.asl

@@ -27,7 +27,7 @@ Scope (\_TZ)
 			Multiply (Arg0, 10, Local0)
 
 			// Convert to Kelvin
-			Add (Local0, 2732, Local0)
+			Local0 += 2732
 
 			Return (Local0)
 		}

src/mainboard/google/jecht/variants/tidus/include/variant/acpi/thermal.asl

@@ -42,7 +42,7 @@ Scope (\_TZ)
 			Multiply (Arg0, 10, Local0)
 
 			// Convert to Kelvin
-			Add (Local0, 2732, Local0)
+			Local0 += 2732
 
 			Return (Local0)
 		}