perf util: Fix NULL check in cpumask_to_cpulist()

perf util: Fix NULL check in cpumask_to_cpulist()

The function cpumask_to_cpulist() allocates memory with calloc() and
stores the result in 'bm', but then incorrectly checks 'cpumask' for
NULL instead of 'bm'.

This means that if the allocation fails, the function will dereference a
NULL pointer when trying to access 'bm'.

Fix the check to test the correct variable 'bm'.

Fixes: d40c68a49f69c9bd ("perf header: Support CPU DOMAIN relation info")
Reviewed-by: Shrikanth Hegde <sshegde@linux.ibm.com>
Signed-off-by: Swapnil Sapkal <swapnil.sapkal@amd.com>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Anubhav Shelat <ashelat@redhat.com>
Cc: Chen Yu <yu.c.chen@intel.com>
Cc: Gautham Shenoy <gautham.shenoy@amd.com>
Cc: Ian Rogers <irogers@google.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@arm.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ravi Bangoria <ravi.bangoria@amd.com>
Cc: Thomas Falcon <thomas.falcon@intel.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>