Expose boot performance metrics via ACPI FPDT

[xen0n]

The table is used by boot performance profiling tools such as systemd-analyze:

https://github.com/systemd/systemd/blob/v259/src/shared/boot-timestamps.c#L21-L26

https://github.com/systemd/systemd/blob/v259/src/shared/acpi-fpdt.c#L108

I believe this should be useful long-term when LoongArch system integrators eventually need to optimize their boot-time performance.

[xry111]

OVMF now supports it: tianocore/edk2#12378

The support for real hardware is under discussion.

[MarsDoge]

This feature has been supported since stable202605.
Tested on the XA61200 board with release version stable202605 :
$ systemd-analyze
Startup finished in 13.559s (firmware) + 7.486s (loader) + 1.520s (kernel) + 2.585s (initrd) + 1min 31.045s (userspace) = 1min 56.196s
graphical.target reached after 8.563s in userspace.

Thanks.