perf tools: Mark split kallsyms DSOs as loaded

perf tools: Mark split kallsyms DSOs as loaded

The maps__split_kallsyms() will split symbols to module DSOs if it comes
from a module.  It also handled some unusual kernel symbols after modules
by creating new kernel maps like "[kernel].0".

But they are pseudo DSOs to have those unexpected symbols.  They should
not be considered as unloaded kernel DSOs.  Otherwise the dso__load()
for them will end up calling dso__load_kallsyms() and then
maps__split_kallsyms() again and again.

Reviewed-by: Ian Rogers <irogers@google.com>
Fixes: 2e538c4a1847291cf ("perf tools: Improve kernel/modules symbol lookup")
Signed-off-by: Namhyung Kim <namhyung@kernel.org>