KVM: selftests: Expand negative testing of guest writes to PERF_CAPABILITIES

Test that the guest can't write 0 to PERF_CAPABILITIES, can't write the
current value, and can't toggle _any_ bits.  There is no reason to special
case the LBR format.

Link: https://lore.kernel.org/r/20230311004618.920745-17-seanjc@google.com


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