better emulate PM1 registers

[pfmooney]

When booting Linux (depending on the kernel version), some ACPI errors are emitted:

[    0.386017][    T1] ACPI Error: Could not enable GlobalLock event (20230628/evxfevnt-182)
[    0.387055][    T1] ACPI Error: No response from Global Lock hardware, disabling lock (20230628/evglock-59)
[    0.926299][    T1] ACPI Error: Could not enable RealTimeClock event (20230628/evxfevnt-182)

The ACPI logic is attempting to enable the SCI bits for GBL_EN and RTC_EN, which we currently pay no heed to. The former would likely be trivial to support, since I do not believe there is Global Lock activity from the firmware, and thus no source for such events. The latter poses more of a challenge, since we have no way of wiring up RTC events into the emulated power management device. Allowing the guest to enable such events might be a cruel lie, if they will never arrive.