mtd: spi-nor: Prepare the introduction of a new locking mechanism

mtd: spi-nor: Prepare the introduction of a new locking mechanism

This commit alone just introduces two new "prepare and lock" pairs of
helpers which do the exact same thing as before. They will soon be
improved in a followup commit which actually brings the logic, but I
figured out it was more readable to do it this way.

One new pair is suffixed _pe which stands for "program and erase" and
hence is being called by spi_nor_write() and spi_nor_erase().

The other pair is suffixed _rd which stands for "read" and hence is
being called by spi_nor_read().

One note however, these extra helpers will need to know the operation
range, so they come with two new parameters to define it. Otherwise
there is no functional change.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/r/20230328154105.448540-6-miquel.raynal@bootlin.com
Signed-off-by: Tudor Ambarus <tudor.ambarus@linaro.org>