eCryptfs: replace magic numbers

Replace some magic numbers with sizeof() equivalents.

Signed-off-by: Michael Halcrow <mhalcrow@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/ecryptfs/crypto.c b/fs/ecryptfs/crypto.c
index a9ca373..e890d59 100644
--- a/fs/ecryptfs/crypto.c
+++ b/fs/ecryptfs/crypto.c
@@ -1426,10 +1426,10 @@
 	u32 header_extent_size;
 	u16 num_header_extents_at_front;
 
-	memcpy(&header_extent_size, virt, 4);
+	memcpy(&header_extent_size, virt, sizeof(u32));
 	header_extent_size = be32_to_cpu(header_extent_size);
-	virt += 4;
-	memcpy(&num_header_extents_at_front, virt, 2);
+	virt += sizeof(u32);
+	memcpy(&num_header_extents_at_front, virt, sizeof(u16));
 	num_header_extents_at_front = be16_to_cpu(num_header_extents_at_front);
 	crypt_stat->num_header_extents_at_front =
 		(int)num_header_extents_at_front;