mtd: rawnand: allow vendors to declare (un)supported features

If SET/GET_FEATURES is available (from the parameter page), use a
bitmap to declare what feature is actually supported.

Initialize the bitmap in the core to support timing changes (only
feature used by the core), also add support for Micron specific features
used in Micron initialization code (in the init routine).

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Signed-off-by: Boris Brezillon <boris.brezillon@bootlin.com>