s390: make setup_randomness work

BugLink: http://bugs.launchpad.net/bugs/1673541

commit da8fd820 upstream.

Commit bcfcbb6b ("s390: add system information as device
randomness") intended to add some virtual machine specific information
to the randomness pool.

Unfortunately it uses the page allocator before it is ready to use. In
result the page allocator always returns NULL and the setup_randomness
function never adds anything to the randomness pool.

To fix this use memblock_alloc and memblock_free instead.

Fixes: bcfcbb6b ("s390: add system information as device randomness")
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>

arch/s390/kernel/setup.c

@@ -805,10 +805,10 @@ static void __init setup_randomness(void)
 {
 	struct sysinfo_3_2_2 *vmms;
 
-	vmms = (struct sysinfo_3_2_2 *) alloc_page(GFP_KERNEL);
-	if (vmms && stsi(vmms, 3, 2, 2) == 0 && vmms->count)
+	vmms = (struct sysinfo_3_2_2 *) memblock_alloc(PAGE_SIZE, PAGE_SIZE);
+	if (stsi(vmms, 3, 2, 2) == 0 && vmms->count)
 		add_device_randomness(&vmms, vmms->count);
-	free_page((unsigned long) vmms);
+	memblock_free((unsigned long) vmms, PAGE_SIZE);
 }
 
 /*