perf/x86: Add structures for the attributes of Hybrid PMUs

Hybrid PMUs have different events and formats. In theory, Hybrid PMU
specific attributes should be maintained in the dedicated struct
x86_hybrid_pmu, but it wastes space because the events and formats are
similar among Hybrid PMUs.

To reduce duplication, all hybrid PMUs will share a group of attributes
in the following patch. To distinguish an attribute from different
Hybrid PMUs, a PMU aware attribute structure is introduced. A PMU type
is required for the attribute structure. The type is internal usage. It
is not visible in the sysfs API.

Hybrid PMUs may support the same event name, but with different event
encoding, e.g., the mem-loads event on an Atom PMU has different event
encoding from a Core PMU. It brings issue if two attributes are
created for them. Current sysfs_update_group finds an attribute by
searching the attr name (aka event name). If two attributes have the
same event name, the first attribute will be replaced.
To address the issue, only one attribute is created for the event. The
event_str is extended and stores event encodings from all Hybrid PMUs.
Each event encoding is divided by ";". The order of the event encodings
must follow the order of the hybrid PMU index. The event_str is internal
usage as well. When a user wants to show the attribute of a Hybrid PMU,
only the corresponding part of the string is displayed.

Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Link: https://lkml.kernel.org/r/1618237865-33448-18-git-send-email-kan.liang@linux.intel.com