s390/crash: remove redundant panic() on save area allocation failure

Make save_area_alloc() return classic NULL on allocation failure.
The only caller smp_save_dump_cpus() does check the return value
already and panics if NULL is returned.
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>

arch/s390/kernel/crash_dump.c

@@ -63,7 +63,7 @@ struct save_area * __init save_area_alloc(bool is_boot_cpu)
 
 	sa = memblock_alloc(sizeof(*sa), 8);
 	if (!sa)
-		panic("Failed to allocate save area\n");
+		return NULL;
 
 	if (is_boot_cpu)
 		list_add(&sa->list, &dump_save_areas);