mtd: rawnand: denali: Delete items from the list in the _remove() path

Denali driver keeps track of devices with a list. Delete items of this
list as long as they are not in use anymore.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Acked-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Link: https://lore.kernel.org/linux-mtd/20200519130035.1883-11-miquel.raynal@bootlin.com