perf/x86: Remove unused variable 'cpu_type'

Since the removal of function x86_pmu_update_cpu_context() by commit
983bd8543b5a ("perf: Rewrite core context handling"), there is no need to
query the type of the hybrid CPU inside function init_hw_perf_events().

Fixes: 983bd8543b5a ("perf: Rewrite core context handling")
Signed-off-by: Rafael Mendonca <rafaelmendsr@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lkml.kernel.org/r/20221028203006.976831-1-rafaelmendsr@gmail.com