drivers: flash: remove W25QXXDV driver

The spi_flash_w25qxxdv driver has been superseded by the generic
spi_nor driver for over a year.  The only non-refactoring change to
the W25Q driver in the last 18 months was done to support a backport
to 1.14.

All devices supported by spi_flash_w25qxxdv driver are expected to be
supported by the spi_nor driver, using the standard `jedec,spi-nor`
devicetree compatible.  No in-tree devicetree files make use of this
driver.

Remove the confusion about which driver to select by removing the
unmaintained redundant driver.

Signed-off-by: Peter Bigot <peter.bigot@nordicsemi.no>
10 files changed