powerpc/nvram: Fix endian issue when using the partition length

When reading partitions, the length has to be translated from
big endian to the endian order of the host. Similarly, when writing
partitions, the length needs to be in big endian order.

The userspace tool 'nvram' needs a similar fix as it is reading
and writing partitions through /dev/nram :

    http://sourceforge.net/p/powerpc-utils/mailman/message/31571277/Signed-off-by: NCedric Le Goater <clg@fr.ibm.com>
Signed-off-by: NBenjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/kernel/nvram_64.c

@@ -223,9 +223,13 @@ static int __init nvram_write_header(struct nvram_partition * part)
 {
 	loff_t tmp_index;
 	int rc;
-	
+	struct nvram_header phead;
+
+	memcpy(&phead, &part->header, NVRAM_HEADER_LEN);
+	phead.length = cpu_to_be16(phead.length);
+
 	tmp_index = part->index;
-	rc = ppc_md.nvram_write((char *)&part->header, NVRAM_HEADER_LEN, &tmp_index); 
+	rc = ppc_md.nvram_write((char *)&phead, NVRAM_HEADER_LEN, &tmp_index);
 
 	return rc;
 }
@@ -505,6 +509,8 @@ int __init nvram_scan_partitions(void)
 
 		memcpy(&phead, header, NVRAM_HEADER_LEN);
 
+		phead.length = be16_to_cpu(phead.length);
+
 		err = 0;
 		c_sum = nvram_checksum(&phead);
 		if (c_sum != phead.checksum) {