[JFFS2] Reduce visibility of raw_node_ref to upper layers of JFFS2 code.

As the first step towards eliminating the ref->next_phys member and saving
memory by using an _array_ of struct jffs2_raw_node_ref per eraseblock,
stop the write functions from allocating their own refs; have them just
_reserve_ the appropriate number instead. Then jffs2_link_node_ref() can
just fill them in.

Use a linked list of pre-allocated refs in the superblock, for now. Once
we switch to an array, it'll just be a case of extending that array.

Signed-off-by: David Woodhouse <dwmw2@infradead.org>

diff --cc fs/jffs2/erase.c
Simple merge

diff --cc fs/jffs2/gc.c
Simple merge

diff --cc fs/jffs2/jffs2_fs_sb.h
Simple merge

diff --cc fs/jffs2/malloc.c
Simple merge

diff --cc fs/jffs2/nodelist.c
Simple merge

diff --cc fs/jffs2/nodelist.h
Simple merge

diff --cc fs/jffs2/nodemgmt.c
Simple merge

diff --cc fs/jffs2/scan.c
Simple merge

diff --cc fs/jffs2/summary.c
Simple merge

diff --cc fs/jffs2/wbuf.c
Simple merge

diff --cc fs/jffs2/write.c
Simple merge

diff --cc fs/jffs2/xattr.c
Simple merge