drivers: flash: add extended operations to Andes XIP driver

Add the extended operations to the Andes XIP flash driver.

The extended operations supports:
 - reading status registers of the flash chip
 - changing status registers of the flash chip
 - software lock of the status registers
 - modifying SPI read command used in memory-mapped mode

Signed-off-by: Dawid Niedzwiecki <dawidn@google.com>