mtd: spinand: Add octal DTR support

mtd: spinand: Add octal DTR support

Create a new bus interface named ODTR for "octal DTR", which matches the
following pattern: 8D-8D-8D.

Add octal DTR support for all the existing core operations. Add a second
set of templates for this bus interface.

Give the possibility for drivers to register their read, write and
update cache variants as well as their vendor specific operations.

Check the SPI controller driver supports all the octal DTR commands that
we might need before switching to the ODTR bus interface.

Make the switch by calling ->configure_chip() with the ODTR
parameter. Fallback in case this step fails.

If someone ever attempts to suspend a chip in octal DTR mode, there are
changes that it will loose its configuration at resume. Prevent any
problem by explicitly switching back to SSDR while suspending. Note:
there is a limitation in the current approach, page I/Os are not
available as the dirmaps will be created for the ODTR bus interface if
that option is supported and not switched back to SSDR during
suspend. Switching them is possible but would be costly and would not
bring anything as right after resuming we will switch again to ODTR. In
case this capability is used for debug, developpers should mind to
destroy and recreate suitable direct mappings.

Finally, as a side effect, we increase the buffer for reading IDs to
6. No device at this point returns 6 bytes, but we support 5 bytes IDs,
which means in octal DTR mode we have no other choice than reading an
even number of bytes, hence 6.

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