KVM: selftests: Assert that full-width PMC writes are supported if PDCM=1

KVM emulates full-width PMC writes in software, assert that KVM reports
full-width writes as supported if PERF_CAPABILITIES is supported.

Link: https://lore.kernel.org/r/20230311004618.920745-11-seanjc@google.com


Signed-off-by: Sean Christopherson <seanjc@google.com>