[JFFS2] Fix write buffer retry case

Correction of retry case to avoid silent failure of rmdir
when jffs2_wbuf_recover GCs the previous entry (+ corresponding
dnode case).

Signed-off-by: Estelle Hammache <estelle.hammache@st.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>