Docs: added ACPI sample SSDT-EHCx_OFF.dsl

Docs/AcpiSamples/SSDT-EHCx_OFF.dsl

+/*
+ * Intel ACPI Component Architecture
+ * AML/ASL+ Disassembler version 20190215 (64-bit version)
+ * Copyright (c) 2000 - 2019 Intel Corporation
+ * 
+ * Disassembling to symbolic ASL+ operators
+ *
+ * Disassembly of iASL8AmXq4.aml, Tue Apr 16 22:05:03 2019
+ *
+ * Original Table Header:
+ *     Signature        "SSDT"
+ *     Length           0x0000005E (94)
+ *     Revision         0x02
+ *     Checksum         0x8F
+ *     OEM ID           "APPLE "
+ *     OEM Table ID     "EHCx_OFF"
+ *     OEM Revision     0x00001000 (4096)
+ *     Compiler ID      "INTL"
+ *     Compiler Version 0x20190215 (538509845)
+ */
+DefinitionBlock ("", "SSDT", 2, "APPLE ", "EHCx_OFF", 0x00001000)
+{
+    Scope (\)
+    {
+        OperationRegion (RCRG, SystemMemory, 0xFED1F418, One)
+        Field (RCRG, DWordAcc, Lock, Preserve)
+        {
+                ,   13, 
+            EH2D,   1, 
+                ,   1, 
+            EH1D,   1
+        }
+
+        Method (_INI, 0, NotSerialized)  // _INI: Initialize
+        {
+            EH1D = One  // Disable EHC1
+            EH2D = One  // Disable EHC2
+        }
+    }
+}
+
+// Attention!
+// Only for 7,8,9-series chipsets and 10.11 and newer!
+//
+// To disable EHC1 and EHC2 - set an option "XHCI Mode" to "Enabled" in yours BIOS.
+// If the "XHCI Mode" option is not available in yours BIOS or works incorrectly, then use this ACPI table.
+// Disabling through BIOS is preferable whenever possible.
+//
+// Note: for 7-series you need to use either "EH1D = One" or "EH2D = One" but not both!
+// This is because only one of the devices (EHC1 or EHC2) is used by macOS. Check the IOReg.