perf pmu: Add PMU alias support

A perf uncore PMU may have two PMU names, a real name and an alias. The
alias is exported at /sys/bus/event_source/devices/uncore_*/alias.
The perf tool should support the alias as well.

Add alias_name in the struct perf_pmu to store the alias. For the PMU
which doesn't have an alias. It's NULL.

Introduce two X86 specific functions to retrieve the real name and the
alias separately.

Only go through the sysfs to retrieve the mapping between the real name
and the alias once. The result is cached in a list, uncore_pmu_list.

Nothing changed for the other ARCHs.

With the patch, the perf tool can monitor the PMU with either the real
name or the alias.

Use the real name,
 $ perf stat -e uncore_cha_2/event=1/ -x,
   4044879584,,uncore_cha_2/event=1/,2528059205,100.00,,

Use the alias,
 $ perf stat -e uncore_type_0_2/event=1/ -x,
   3659675336,,uncore_type_0_2/event=1/,2287306455,100.00,,

Committer notes:

Rename 'struct perf_pmu_alias_name' to 'pmu_alias', the 'perf_' prefix
should be used for libperf, things inside just tools/perf/ are being
moved away from that prefix.

Also 'pmu_alias' is shorter and reflects the abstraction.

Also don't use 'pmu' as the name for variables for that type, we should
use that for the 'struct perf_pmu' variables, avoiding confusion. Use
'pmu_alias' for 'struct pmu_alias' variables.

Co-developed-by: Jin Yao <[email protected]>
Co-developed-by: Arnaldo Carvalho de Melo <[email protected]>
Signed-off-by: Kan Liang <[email protected]>
Reviewed-by: Andi Kleen <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: John Garry <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Riccardo Mancini <[email protected]>
Link: http://lore.kernel.org/lkml/[email protected]
Signed-off-by: Jin Yao <[email protected]>
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

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