src/ec/acpi/ec.asl: Convert to ASL 2.0

Change-Id: I078ca86cf9e948d4dd4338fca842ae3e580228ef
Signed-off-by: Elyes HAOUAS <ehaouas@noos.fr>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/50316
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Angel Pons <th3fanbus@gmail.com>

src/ec/acpi/ec.asl

@@ -68,7 +68,7 @@ Method (SEND_EC_COMMAND, 1)
 {
 	Local0 = WAIT_EC_SC (EC_IBF, 0)
 	If (!Local0) {
-		Store (Arg0, EC_SC)
+		EC_SC = Arg0
 	}
 	Return (Local0)
 }