KVM: selftests: Remove dead code in Intel PMU counters test

KVM: selftests: Remove dead code in Intel PMU counters test

Drop the local "nr_arch_events" in the Intel PMU counters test as the test
asserts that "nr_arch_events <= NR_INTEL_ARCH_EVENTS", and then sets
nr_arch_events to the max of the two.  I.e. nr_arch_events is guaranteed
to be NR_INTEL_ARCH_EVENTS for the meat of the test, just use
NR_INTEL_ARCH_EVENTS directly.

No functional change intended.

Link: https://lore.kernel.org/r/20250117234204.2600624-4-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>