kontron/986lcd-m: 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 and remark:
dsdt.aml   1451:  Method (_CRS, 0)
Remark   2120 -             ^ Control Method should be made Serialized
(due to creation of named objects within)
dsdt.aml   1460:  Method (_REG, 2)
Warning  3079 -             ^ _REG has no corresponding Operation Region

Change-Id: I4aa59468a89c4013146ab34004476a0968c60707
Signed-off-by: Martin Roth <martinroth@google.com>
Reviewed-on: https://review.coreboot.org/12521
Reviewed-by: Patrick Georgi <pgeorgi@google.com>
Tested-by: build bot (Jenkins)

src/mainboard/kontron/986lcd-m/Kconfig

@@ -42,8 +42,4 @@ config VGA_BIOS_FILE
 	string
 	default "amipci_01.20"
 
-# TODO: Remove this when platform ASL is fixed
-config IASL_WARNINGS_ARE_ERRORS
-	def_bool n
-
 endif # BOARD_KONTRON_986LCD_M

src/mainboard/kontron/986lcd-m/acpi/ec.asl

@@ -18,7 +18,13 @@ Device(EC0)
 	Name (_HID, EISAID("PNP0C09"))
 	Name (_UID, 1)
 
-	Method (_CRS, 0)
+	// _REG method requires that an operation region is defined.
+	OperationRegion (ERAM, EmbeddedControl, 0x00, 0xff)
+	Field (ERAM, ByteAcc, Lock, Preserve)
+	{
+	}
+
+	Method (_CRS, 0, Serialized)
 	{
 		Name (ECMD, ResourceTemplate()
 		{