The PKRU state size is 4 bytes, its support makes the XSAVE area size
non-multiple of 64 bytes. Thereafter, the user state save area is
misaligned, which triggers assertion in the debugging kernels, or
segmentation violation on accesses for non-debugging configs.

Force the desired alignment of the user save area as the fix
(workaround is to disable bit 9 in the hw.xsave_mask loader tunable).
This correction is required for booting on the upcoming Intel' Purley
platform.

Reported and tested by: "Pieper, Jeffrey E" <jeffrey.e.pieper@intel.com>,
jimharris
Sponsored by: The FreeBSD Foundation
MFC after: 3 days