[JFFS2] fix sparse warning in write.c

fs/jffs2/write.c:585:28: warning: symbol 'fd' shadows an earlier one
fs/jffs2/write.c:536:27: originally declared here

No need to redeclare fd, use the original one, after this point,
fd is always reassigned before it used again.

Signed-off-by: Harvey Harrison <harvey.harrison@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>