man: Fix uninitialized err_entry

fi_cq_readerr is no longer called on uninitialized
err_data and err_data_size in fi_setup.7.md.

Signed-off-by: Rémi Dehenne <remi.dehenne@cea.fr>

man/fi_setup.7.md

@@ -947,8 +947,12 @@ struct fi_cq_err_entry {
 /* Sample error handling */
 struct fi_cq_msg_entry entry;
 struct fi_cq_err_entry err_entry;
+char err_data[256];
 int ret;
 
+err_entry.err_data = err_data;
+err_entry.err_data_size = 256;
+
 ret = fi_cq_read(cq, &entry, 1);
 if (ret == -FI_EAVAIL)
     ret = fi_cq_readerr(cq, &err_entry, 0);