mtd: spinand: Drop ECC dirmaps

Direct mappings are very static concepts, which allow us to reuse a
template to perform reads or writes in a very efficient manner after a
single initialization. With the introduction of pipelined ECC engines
for SPI controllers, the need to differentiate between an operation with
and without correction has arised. The chosen solution at that time has
been to create new direct mappings for these operations, jumping from 2
to 4 dirmaps per target. Enabling ECC was done by choosing the correct
dirmap.

Today, we need to further parametrize dirmaps. With the goal to enable
continuous reads on a wider range of devices, we will need more
flexibility regarding the read from cache operation template to pick at
run time, for instance to use shorter "continuous read from cache"
variants.

We could create other direct mappings, but it would increase the matrix
by a power of two, bringing the theoretical number of dirmaps to
8 (read/write, ecc, shorter read variants) per target. This grow is not
sustainable, so let's change how dirmaps work - a little bit.

Operations already carry an ECC parameter, use it to indicate whether
error correction is required or not. In practice this change happens
only at the core level, SPI controller drivers do not care about the
direct mapping structure in this case, they just pick whatever is in the
template as a base. As a result, we allow the core to dynamically change
the content of the templates.

He who can do more can do less, so during the checking steps, make sure
to enable the ECC requirement just for the time of the checks.

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

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