i386: acpi: Don't build HPET ACPI entry if HPET is disabled

i386: acpi: Don't build HPET ACPI entry if HPET is disabled

Omit HPET AML if the HPET is disabled, QEMU is not emulating it and the
guest may get confused by seeing HPET in the ACPI tables without a
"physical" device present.

The change of DSDT when -no-hpet is as follows.

@@ -141,47 +141,6 @@ DefinitionBlock ("", "DSDT", 1, "BOCHS "
         }
     }

-    Scope (_SB)
-    {
-        Device (HPET)
-        {
-            Name (_HID, EisaId ("PNP0103") /* HPET System Timer */)  // _HID: Hardware ID
-            Name (_UID, Zero)  // _UID: Unique ID
-            OperationRegion (HPTM, SystemMemory, 0xFED00000, 0x0400)
-            Field (HPTM, DWordAcc, Lock, Preserve)
-            {
-                VEND,   32,
-                PRD,    32
-            }
-
-            Method (_STA, 0, NotSerialized)  // _STA: Status
-            {
-                Local0 = VEND /* \_SB_.HPET.VEND */
-                Local1 = PRD /* \_SB_.HPET.PRD_ */
-                Local0 >>= 0x10
-                If (((Local0 == Zero) || (Local0 == 0xFFFF)))
-                {
-                    Return (Zero)
-                }
-
-                If (((Local1 == Zero) || (Local1 > 0x05F5E100)))
-                {
-                    Return (Zero)
-                }
-
-                Return (0x0F)
-            }
-
-            Name (_CRS, ResourceTemplate ()  // _CRS: Current Resource Settings
-            {
-                Memory32Fixed (ReadOnly,
-                    0xFED00000,         // Address Base
-                    0x00000400,         // Address Length
-                    )
-            })
-        }
-    }
-
     Scope (_SB.PCI0)
     {
         Device (ISA)

Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Igor Mammedov <imammedo@redhat.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Message-Id: <66114dead09232d04891b9e5f5a4081e85cc2c4d.1613615732.git.isaku.yamahata@intel.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>