ec/quanta/ene_kb3940q/acpi: Replace Decrement() with ASL 2.0 syntax

Replace `Decrement (a)` with `a--`.

Change-Id: I2105c22d15d4f078270911a7fa7290b3a9b6b841
Signed-off-by: Felix Singer <felixsinger@posteo.net>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/60591
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: HAOUAS Elyes <ehaouas@noos.fr>

src/ec/quanta/ene_kb3940q/acpi/ec.asl

@@ -194,7 +194,7 @@ Device (EC0)
 		Store(\_SB.CP00._PPC, Local0)
 
 		If(Local0) {
-			Decrement(Local0)
+			Local0--
 			\PPCN ()
 		}