perf/amd/uncore: Simplify code, use free_percpu()'s built-in check for NULL

mainline inclusion
from mainline-v5.15-rc1
commit 6cf295b2
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I65D55


CVE: NA

--------------------------------

free_percpu() has its own check for NULL, no need to open-code it.

Signed-off-by: Kim Phillips <kim.phillips@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20210817221048.88063-5-kim.phillips@amd.com


Signed-off-by: Xie Haocheng <haocheng.xie@amd.com>