perf symbol-elf: dso__load_sym_internal() reference count fixes

dso__load_sym_internal() passed curr_mapp as an out argument to
dso__process_kernel_symbol(). The out argument was never used so remove
it to simplify the reference counting logic.

Simplify reference counting issues with curr_dso by ensuring the value
it points to has a +1 reference count, and then putting as
necessary.

This avoids some reference counting games when the dso is created making
the code more obviously correct with some possible introduced overhead
due to the reference counting get/puts.

This, however, silences reference count checking and we can always
optimize from a seemingly correct point.

Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Cc: Changbin Du <changbin.du@huawei.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Tiezhu Yang <yangtiezhu@loongson.cn>
Link: https://lore.kernel.org/r/20240506180104.485674-4-irogers@google.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>