ck/aarch64: Specify output operands for ck_pr_md_store_*

ck/aarch64: Specify output operands for ck_pr_md_store_*

This is a backport of upstream commit d1e9f03b89:

    ck_pr/aarch64: Specify output operands for ck_pr_md_store_*

    As in commit 2f9acab, we want to specify output operand widths so that
    MSAN compiler instrumentation correctly updates the shadow map.  In
    particular, LLVM's implementation depends on having type information for
    output operands, even when that's not otherwise necessary.  Without it,
    KMSAN in FreeBSD generates false positives on aarch64.

Reviewed by:	cognet
MFC after:	2 weeks
Sponsored by:	Klara, Inc.
Sponsored by:	Juniper Networks, Inc.