iwave/IWRainBowG6: Fix IASL warning and remark

- Add an empty Operating Region for the empty _REG method
- Serialize _CRS Method
- Remove Kconfig default disabling IASL warnings as errors

Fixes IASL Warning:
dsdt.aml   1362:  Method (_REG, 2)
Warning  3079 -             ^ _REG has no corresponding Operation Region

Fixes IASL remark:
dsdt.aml   1353:  Method (_CRS, 0)
Remark   2120 -             ^ Control Method should be made Serialized
(due to creation of named objects within)

Change-Id: Iff01613a6e3238469c1fcb8d74f5e98d18420aaf
Signed-off-by: Martin Roth <martinroth@google.com>
Reviewed-on: https://review.coreboot.org/12515
Tested-by: build bot (Jenkins)
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

src/mainboard/iwave/iWRainbowG6/Kconfig

@@ -28,10 +28,6 @@ config IRQ_SLOT_COUNT
 	int
 	default 10
 
-# TODO: Remove this when platform ASL is fixed
-config IASL_WARNINGS_ARE_ERRORS
-	def_bool n
-
 # This mainboard might have a higher clocked UART or might not be able to run
 # serial output at 115200 baud
 

src/mainboard/iwave/iWRainbowG6/acpi/ec.asl

@@ -19,7 +19,13 @@ Device(EC0)
 	Name (_HID, EISAID("PNP0C09"))
 	Name (_UID, 1)
 
-	Method (_CRS, 0)
+	// _REG method requires that an operation region be defined.
+	OperationRegion (ERAM, EmbeddedControl, 0x00, 0xff)
+	Field (ERAM, ByteAcc, Lock, Preserve)
+	{
+	}
+
+	Method (_CRS, 0, Serialized)
 	{
 		Name (ECMD, ResourceTemplate()
 		{