intel/intelpmc: Add Intel PMC Core driver

Add driver for Intel Power Management Controller (PMC) found on Sunrise Point PCH chipsets.
This device exposes S0ix sleep state residency counters and powe

intel/intelpmc: Add Intel PMC Core driver

Add driver for Intel Power Management Controller (PMC) found on Sunrise Point PCH chipsets.
This device exposes S0ix sleep state residency counters and power management status.

Sysctls provided:
dev.intelpmc.0.slp_s0_residency_us - Time in deepest sleep (us)
dev.intelpmc.0.ltr_ignore - LTR ignore mask
dev.intelpmc.0.pm_cfg - PM configuration register
dev.intelpmc.0.pm_sts - PM status register
dev.intelpmc.0.access_denied - Firmware lock status

Supported devices for now:
- Sunrise Point-LP (0x9D21)
- Sunrise Point-H (0xA121)

Note: Later PCH generations (Cannon Lake, Tiger Lake, ect.) have different PMC register layouts according to the datasheet and would need per-generation tables.
I avoided adding untested hardware in case they have a quirk.

Reviewed by: olce, adrian
Differential Revision: https://reviews.freebsd.org/D54881

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