mtd: rawnand: Change Kconfig titles and re-order a bit the list

This list is a mess, while some items should probably not be in the
raw/ sub-directory, others are definitely at the right place but not
with the right description. Write uniform titles and group IPs by
vendor.

NAND controllers will appear under the list named "Raw/parallel NAND
flash controllers" while the other drivers will appear under
"Misc". Software ECC engines will later be moved out of the raw/
directory.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>