MFC: add hooks for HPET missed in previous commit

sys/dev/acpica/acpi.c

@@ -484,6 +484,7 @@ acpi_attach(device_t dev)
      * a problem but should be addressed eventually.
      */
     acpi_ec_ecdt_probe(dev);
+    acpi_hpet_table_probe(dev);
 
     /* Bring device objects and regions online. */
     if (ACPI_FAILURE(status = AcpiInitializeObjects(flags))) {

sys/dev/acpica/acpivar.h

@@ -405,6 +405,8 @@ int		acpi_battery_get_battinfo(device_t dev,
 
 /* Embedded controller. */
 void		acpi_ec_ecdt_probe(device_t);
+/* HPET table probe*/
+void		acpi_hpet_table_probe(device_t);
 
 /* AC adapter interface. */
 int		acpi_acad_get_acline(int *);