v3d: Actually put the "%s" in the snprintf.

I missed an important part when porting the change over, fixing my
compiler warning but breaking -Werror=format-security.

Fixes: e6ff5ac446 ("v3d: use snprintf(..., "%s", ...) instead of strncpy")
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=107443

src/broadcom/cle/v3d_decoder.c

@@ -834,7 +834,7 @@ iter_advance_field(struct v3d_field_iterator *iter)
 
         iter->field = iter->group->fields[iter->field_iter++];
         if (iter->field->name)
-                snprintf(iter->name, sizeof(iter->name), iter->field->name);
+                snprintf(iter->name, sizeof(iter->name), "%s", iter->field->name);
         else
                 memset(iter->name, 0, sizeof(iter->name));
         iter->offset = iter_group_offset_bits(iter, iter->group_iter) / 8 +