x86/cpu: Add get_llc_id() helper function

mainline inclusion
from mainline-v5.15-rc1
commit 9164d949
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I65D55


CVE: NA

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

Factor out a helper function rather than export cpu_llc_id, which is
needed in order to be able to build the AMD uncore driver as a module.

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/20210817221048.88063-7-kim.phillips@amd.com


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