tools/mm: free the allocated memory

The comm_str memory needs to be freed if the search_pattern function call
fails in get_comm

[akpm@linux-foundation.org: fix whitespace]
Link: https://lkml.kernel.org/r/20241022012526.7597-1-liujing@cmss.chinamobile.com


Signed-off-by: Liu Jing <liujing@cmss.chinamobile.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>