ACPICA: Fail AcpiEnable if ACPI tables not loaded.

AcpiEnable will now fail if all of the required ACPI tables are not
loaded (FADT, FACS, DSDT). BZ 477

Signed-off-by: Alexey Starikovskiy <alexey.y.starikovskiy@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>

drivers/acpi/tables/tbutils.c

@@ -52,6 +52,29 @@ static acpi_physical_address
 acpi_tb_get_root_table_entry(u8 * table_entry,
 			     acpi_native_uint table_entry_size);
 
+/*******************************************************************************
+ *
+ * FUNCTION:    acpi_tb_tables_loaded
+ *
+ * PARAMETERS:  None
+ *
+ * RETURN:      TRUE if required ACPI tables are loaded
+ *
+ * DESCRIPTION: Determine if the minimum required ACPI tables are present
+ *              (FADT, FACS, DSDT)
+ *
+ ******************************************************************************/
+
+u8 acpi_tb_tables_loaded(void)
+{
+
+	if (acpi_gbl_root_table_list.count >= 3) {
+		return (TRUE);
+	}
+
+	return (FALSE);
+}
+
 /*******************************************************************************
  *
  * FUNCTION:    acpi_tb_print_table_header