sb/intel/i82371eb/acpi: Replace Decrement() with ASL 2.0 syntax

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

Change-Id: Iae59333a910cc913bb28ed5436c124b2ab282435
Signed-off-by: Felix Singer <felixsinger@posteo.net>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/60587
Reviewed-by: HAOUAS Elyes <ehaouas@noos.fr>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/southbridge/intel/i82371eb/acpi/intx.asl

@@ -40,7 +40,7 @@ Device(intx) {						\
 		/* Use lowest available IRQ */		\
 		FindSetRightBit(IRQM, Local0)		\
 		if (Local0) {				\
-			Decrement(Local0)		\
+			Local0--			\
 		}					\
 		Store(Local0, pinx)			\
 	}						\

src/southbridge/intel/i82371eb/acpi/pirq.asl

@@ -50,7 +50,7 @@ Device(intx) {						\
 		/* Use lowest available IRQ */		\
 		FindSetRightBit(IRQM, Local0)		\
 		if (Local0) {				\
-			Decrement(Local0)		\
+			Local0--			\
 		}					\
 		Store(Local0, pinx)			\
 	}						\