arm64: Enable MOPS in userspace

[sarah.walker2_arm.com]

Summary

Detect presence of FEAT_MOPS, and enable instruction set and set HWCAP2 flag
if present.

Add handler for MOE exceptions.

Sponsored by: Arm Ltd

[andrew]

sys/arm64/arm64/machdep.c

240

Do we need an isb here and below? I assume it's probably safe for userspace only MOPS. In the kernel I expect we would need it as there may not be a context synchronising event before a MOPS instruction is used.

sys/arm64/include/armreg.h

603–606

In the Arm ARM M.a.a there is a single FormatOption field holding the old OptionA and WrongOption fields (bits 17:16).

[sarah.walker2_arm.com]

Address review comments. Update SHA IFUNC usage.

[sarah.walker2_arm.com]

Address review comments.

[jrtc27]

sys/arm64/arm64/identcpu.c

1098–1099

Indented with spaces not tabs

[jrtc27]

sys/arm64/include/armreg.h

603

This define through OPTION_B2 uses spaces not tabs between the name and value

604

The 5 lines starting here exceed 80 chars, though there are already various violations of that in this file...

680

Uses spaces not tab before comment

[sarah.walker2_arm.com]

Address review comments.