perf unwind-libunwind: Add malloc() failure handling

Add malloc() failure handling in unread_unwind_spec_debug_frame().
This make caller find_proc_info() works well when the allocation failure.

Signed-off-by: Yunseong Kim <yskelg@gmail.com>
Reviewed-by: Ian Rogers <irogers@google.com>
Cc: Ravi Bangoria <ravi.bangoria@amd.com>
Cc: Austin Kim <austindh.kim@gmail.com>
Cc: shjy180909@gmail.com
Cc: Ze Gao <zegao2021@gmail.com>
Cc: Leo Yan <leo.yan@linux.dev>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Link: https://lore.kernel.org/r/20240619204211.6438-2-yskelg@gmail.com