s390/vmcp: correct early_param handling

Check "p" is not NULL before passing it to memparse, which doesn't
handle that case explicitly.

Signed-off-by: Vasily Gorbik <[e-mail]>

drivers/s390/char/vmcp.c

···
 
 static int __init early_parse_vmcp_cma(char *p)
 {
+	if (!p)
+		return 1;
 	vmcp_cma_size = ALIGN(memparse(p, NULL), PAGE_SIZE);
 	return 0;
 }