airoha: spi: snfi driver fixes & improvements

airoha: spi: snfi driver fixes & improvements

This patch series greatly improve airoha snfi driver and fix a
number of serious bugs.

Fixed bugs:
 * Fix reading/writing of flashes with more than one plane per lun
 * Fill the buffer with 0xff before writing
 * Fix reading of flashes supporting continuous reading mode
 * Fix error paths

Improvements:
 * Add support of dual/quad wires spi modes in exec_op(). This also
   fix flash reading/writing if dirmap can't be created.
 * Support of dualio/quadio flash reading commands

Signed-off-by: Mikhail Kshevetskiy <[email protected]>
Link: https://github.com/openwrt/openwrt/pull/20295
Signed-off-by: Robert Marko <[email protected]>