asus/m2v: Make _CRS methods serialized

Address the iasl 20160108-64 (Ubuntu 16.04) warnings below.

```
Intel ACPI Component Architecture
ASL+ Optimizing Compiler version 20160108-64
Copyright (c) 2000 - 2016 Intel Corporation

dsdt.aml    245:      Method (_CRS, 0, NotSerialized)
Remark   2120 -                 ^ Control Method should be made Serialized (due to creation of named objects within)

dsdt.aml    262:      Method (_CRS, 0, NotSerialized)
Remark   2120 -                 ^ Control Method should be made Serialized (due to creation of named objects within)

dsdt.aml    277:      Method (_CRS, 0, NotSerialized)
Remark   2120 -                 ^ Control Method should be made Serialized (due to creation of named objects within)

dsdt.aml    295:    Method(_CRS, 0) {
Remark   2120 -              ^ Control Method should be made Serialized (due to creation of named objects within)
```

Change-Id: Id5b0f33fba8ea25e4a6aa4f01c69a69aaf5aef23
Signed-off-by: Paul Menzel <pmenzel@molgen.mpg.de>
Reviewed-on: https://review.coreboot.org/18323
Tested-by: build bot (Jenkins)
Reviewed-by: Tobias Diedrich <ranma+coreboot@tdiedrich.de>
Reviewed-by: Martin Roth <martinroth@google.com>
diff --git a/src/mainboard/asus/m2v/dsdt.asl b/src/mainboard/asus/m2v/dsdt.asl
index bfa3ba4..0753082 100644
--- a/src/mainboard/asus/m2v/dsdt.asl
+++ b/src/mainboard/asus/m2v/dsdt.asl
@@ -348,7 +348,7 @@
 					{
 						Return (0x0f)
 					}
-					Method (_CRS, 0, NotSerialized)
+					Method (_CRS, 0, Serialized)
 					{
 						Name (TMP, ResourceTemplate () {
 							IO (Decode16, 0x0060, 0x0060, 0x01, 0x01)
@@ -367,7 +367,7 @@
 					{
 						Return (0x0f)
 					}
-					Method (_CRS, 0, NotSerialized)
+					Method (_CRS, 0, Serialized)
 					{
 						Name (TMP, ResourceTemplate () {
 						     IRQNoFlags () {12}
@@ -384,7 +384,7 @@
 					{
 						Return (0x0f)
 					}
-					Method (_CRS, 0, NotSerialized)
+					Method (_CRS, 0, Serialized)
 					{
 						Name (TMP, ResourceTemplate () {
 							IO (Decode16, 0x0378, 0x0378, 0x01, 0x08)
@@ -406,7 +406,7 @@
 
 			External(TOM1) /* top of memory below 4GB */
 
-			Method(_CRS, 0) {
+			Method(_CRS, 0, Serialized) {
 				Name(TMP, ResourceTemplate() {
 					WordBusNumber(ResourceProducer, MinFixed, MaxFixed, PosDecode,
 						0x0000,             // Granularity