perf pmu: Handle memory failure in tool_pmu__new()

perf pmu: Handle memory failure in tool_pmu__new()

On linux-next
commit 72c6f57a4193 ("perf pmu: Dynamically allocate tool PMU")
allocated PMU named "tool" dynamicly. However that allocation
can fail and a NULL pointer is returned. That case is currently
not handled and would result in an invalid address reference.
Add a check for NULL pointer.

Fixes: 72c6f57a4193 ("perf pmu: Dynamically allocate tool PMU")
Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
Reviewed-by: James Clark <james.clark@linaro.org>
Link: https://lore.kernel.org/r/20250319122820.2898333-1-tmricht@linux.ibm.com
Signed-off-by: Namhyung Kim <namhyung@kernel.org>