[JFFS2] Remove number of pointer dereferences in fs/jffs2/summary.c

Reduce the nr.  of pointer dereferences in fs/jffs2/summary.c

Benefits:
 - micro speed optimization due to fewer pointer derefs
 - generated code is slightly smaller
 - better readability

(The first two sound like a compiler problem but I'll go with the third. dwmw2).

Signed-off-by: Jesper Juhl <jesper.juhl@gmail.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>