Handle Skylake-X errata SKZ63.

SKZ63 Processor May Hang When Executing Code In an HLE Transaction
Region

Problem: Under certain conditions, if the processor acquires an HLE
(Hardware Lock Elision) lock via the XACQUIRE instruction in the Host
Physical Address range between 40000000H and 403FFFFFH, it may hang
with an internal timeout error (MCACOD 0400H) logged into
IA32_MCi_STATUS.

Move the pages from the range into the blacklist. Add a tunable to
not waste 4M if local DoS is not the issue.

Reviewed by: markj
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D15001