Add WRITE_LIFE_HINT_NR into the rw_hint enum to define the number of values write life time hints can be set to. This is useful for e.g. file systems which may want to map these values to allocation groups. Signed-off-by: Hans Holmberg <hans.holmberg@wdc.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Carlos Maiolino <cem@kernel.org>