ACPICA: Split out PM1 status registers from the FADT

Add new globals for the PM1 status registers (A/B), similar to the
way the PM1 enable registers are handled. Instead of overloading
the FADT Event Register blocks. This makes the code clearer and
less prone to error.

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