1: shadow: split get_unsafe() invocations
2: shadow: avoid sizeof(this_cpu(...))
3: P2M: split a read_atomic() invocation
4: PV: split a get_unsafe() invocation

This takes care of all 77(?) violations of this rule, according to
https://gitlab.com/xen-project/hardware/xen-staging/-/pipelines/2543797752.

Jan