ACPICA: Update a comment.

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

include/acpi/actypes.h

@@ -48,7 +48,8 @@
 
 /*
  * ACPI_MACHINE_WIDTH must be specified in an OS- or compiler-dependent header
- * and must be either 16, 32, or 64
+ * and must be either 32 or 64. 16-bit ACPICA is no longer supported, as of
+ * 12/2006.
  */
 #ifndef ACPI_MACHINE_WIDTH
 #error ACPI_MACHINE_WIDTH not defined