KVM: selftests: Reduce number of "unavailable PMU events" combos tested

KVM: selftests: Reduce number of "unavailable PMU events" combos tested

Reduce the number of combinations of unavailable PMU events masks that are
testing by the PMU counters test.  In reality, testing every possible
combination isn't all that interesting, and certainly not worth the tens
of seconds (or worse, minutes) of runtime.  Fully testing the N^2 space
will be especially problematic in the near future, as 5! new arch events
are on their way.

Use alternating bit patterns (and 0 and -1u) in the hopes that _if_ there
is ever a KVM bug, it's not something horribly convoluted that shows up
only with a super specific pattern/value.

Reported-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
Reviewed-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
Tested-by: Dapeng Mi <dapeng1.mi@linux.intel.com>
Link: https://lore.kernel.org/r/20250919214648.1585683-4-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>