perf jevents: Add common software event json

perf jevents: Add common software event json

Add json for software events so that in perf list the events can have
a description.  Common json exists for the tool PMU but it has no
sysfs equivalent. Modify the map_for_pmu code to return the common map
(rather than an architecture specific one) when a PMU with a common
name is being looked for, this allows the events to be found.

Signed-off-by: Ian Rogers <irogers@google.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Link: https://lore.kernel.org/r/20250725185202.68671-3-irogers@google.com
Signed-off-by: Namhyung Kim <namhyung@kernel.org>