UPSTREAM: arm64: perf: Add event descriptions

UPSTREAM: arm64: perf: Add event descriptions

Add additional information about the ARM architected hardware events
to make counters self describing. This makes the hardware PMUs easier
to use as perf list contains possible events instead of users having
to refer to documentation like the ARM TRMs.

Change-Id: Idb004bb6d9889f8e63f518d105e238d43956b561
Signed-off-by: Drew Richardson <drew.richardson@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Huang, Tao <huangtao@rock-chips.com>
(cherry picked from commit 9e9caa6a496174e53d7753baa4779717771da4a7)