[PATCH 11/14] fix memory leak in init_xen_crash_info()

Found using -fanalyzer

makedumpfile.c: In function ‘init_xen_crash_info’:
makedumpfile.c:9495:17: warning: leak of ‘buf’ [CWE-401] [-Wanalyzer-malloc-leak]
 9495 |                 return FALSE;
      |                 ^~~~~~

Signed-off-by: Philipp Rudo <prudo@redhat.com>