MFC r340008, r340013

r340008:
Add the ARMv8.3 HCR_EL2 register fields.

Sponsored by: DARPA, AFRL

r340013:
Add the ARMv8.3 SCTLR_EL1 fields.

While here tag which architecture release fields were added and remove a
field that only existed in very early releases of the ARMv8 spec.

Sponsored by: DARPA, AFRL