sio/winbond/w83667hg-a/acpi: Replace Store(a,b) with ASL 2.0 syntax

Replace `Store (a, b)` with `b = a`.

Change-Id: I3809880312af4736407e361da53f0424280e43d4
Signed-off-by: Felix Singer <felixsinger@posteo.net>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/70680
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Elyes Haouas <ehaouas@noos.fr>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Reviewed-by: Eric Lai <eric_lai@quanta.corp-partner.google.com>

src/superio/winbond/w83667hg-a/ps2_controller.asl

@@ -45,14 +45,14 @@
 		Method(_STA, 0)
 		{
 			/* Access SuperIO ACPI device */
-			Store(0x87, SIOI)
-			Store(0x87, SIOI)
+			SIOI = 0x87
+			SIOI = 0x87
 
 			/* Read Pin56 function select */
 			And(CR2A, 0x2, Local0)
 
 			/* Restore default SuperIO access */
-			Store(0xAA, SIOI)
+			SIOI = 0xAA
 
 			if (Local0 == 0) {
 				/* Mouse function selected */