drivers: flash: nrf_qspi: rework handling of quad-enable bit

Kconfig allowed selecting any bit in the status register as the QE
bit, and defaulted it to 6.  Devices need not require a QE bit at all,
and where JESD216 defines QE bit location the only place in first SR
byte that it can be is bit 6.  Further, the code unconditionally wrote
the value 0x40 without respecting configuration of other bits.  Some
of those bits control write protection of block-protected areas and
should not be changed.

Remove the Kconfig, instead using the jedec,jesd216-controlled
devicetree property.  Allow the driver to recognize whether or not
setting the bit is required, and when it is only use bit 6.  Only
update if the setting does not match the configuration.

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