ACPICA: Fix table compare code, length then data

Split the ACPI table compare. First check that the lengths match
exactly. Then compare the data.

Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Lin Ming <ming.m.lin@intel.com>
Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>