s390/ipl: add missing secure/has_secure file to ipl type 'unknown'

OS installers are relying on /sys/firmware/ipl/has_secure to be
present on machines supporting secure boot. This file is present
for all IPL types, but not the unknown type, which prevents a secure
installation when an LPAR is booted in HMC via FTP(s), because
this is an unknown IPL type in linux. While at it, also add the secure
file.

Fixes: c9896ac ("s390/ipl: Provide has_secure sysfs attribute")
Cc: stable@vger.kernel.org
Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>

arch/s390/kernel/ipl.c

@@ -640,6 +640,8 @@ static struct attribute_group ipl_ccw_attr_group_lpar = {
 
 static struct attribute *ipl_unknown_attrs[] = {
 	&sys_ipl_type_attr.attr,
+	&sys_ipl_secure_attr.attr,
+	&sys_ipl_has_secure_attr.attr,
 	NULL,
 };