drivers perf: remove unused field pmu_node

The driver does not use the pmu_node field, so remove it.

Signed-off-by: Yunhui Cui <cuiyunhui@bytedance.com>
Reviewed-by: Shuai Xue <xueshuai@linux.alibaba.com>
Link: https://lore.kernel.org/r/20240919034601.2453-1-cuiyunhui@bytedance.com


Signed-off-by: Will Deacon <will@kernel.org>