zipl: secure boot - verify load address

To ensure that only verified code is executed the stage 3 loader has
to check if the load psw points to an address that has previously been
verified by the machine loader.

If secure boot is enabled the IPL process will only continue if the
verification was successful.

Signed-off-by: Stefan Haberland <sth@linux.ibm.com>
Acked-by: Peter Oberparleiter <oberpar@linux.ibm.com>
Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>

zipl/boot/error.h

@@ -31,6 +31,9 @@
 /* Internal error */
 #define EINTERNAL		0x00004511
 
+/* Secure IPL error */
+#define ESECUREBOOT		0x00004512
+
 /* kdump: No operating system information was found */
 #define EOS_INFO_MISSING	0x00004520