[JFFS2] Fix cross-endian build.

When compiling a LE-capable JFFS2 on PowerPC, wbuf.c fails to compile:

fs/jffs2/wbuf.c:973: error: braced-group within expression allowed only inside a function
fs/jffs2/wbuf.c:973: error: initializer element is not constant
fs/jffs2/wbuf.c:973: error: (near initialization for ‘oob_cleanmarker.magic’)
fs/jffs2/wbuf.c:974: error: braced-group within expression allowed only inside a function
fs/jffs2/wbuf.c:974: error: initializer element is not constant
fs/jffs2/wbuf.c:974: error: (near initialization for ‘oob_cleanmarker.nodetype’)
fs/jffs2/wbuf.c:975: error: braced-group within expression allowed only inside a function
fs/jffs2/wbuf.c:976: error: initializer element is not constant
fs/jffs2/wbuf.c:976: error: (near initialization for ‘oob_cleanmarker.totlen’)

Provide constant_cpu_to_je{16,32} functions, and use them for initialising the
offending structure.

Signed-off-by: David Woodhouse <dwmw2@infradead.org>
diff --git a/fs/jffs2/wbuf.c b/fs/jffs2/wbuf.c
index f9da0e7..f87f11a 100644
--- a/fs/jffs2/wbuf.c
+++ b/fs/jffs2/wbuf.c
@@ -970,9 +970,9 @@
 
 static const struct jffs2_unknown_node oob_cleanmarker =
 {
-	.magic = cpu_to_je16(JFFS2_MAGIC_BITMASK),
-	.nodetype = cpu_to_je16(JFFS2_NODETYPE_CLEANMARKER),
-	.totlen = cpu_to_je32(8)
+	.magic = constant_cpu_to_je16(JFFS2_MAGIC_BITMASK),
+	.nodetype = constant_cpu_to_je16(JFFS2_NODETYPE_CLEANMARKER),
+	.totlen = constant_cpu_to_je32(8)
 };
 
 /*