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QSPI U-boot support

Host processor is connected to serial flash device via qpsi
interface. QSPI is a kind of spi module that allows single,
dual and quad read access to external spi devices. The module
has a memory mapped interface which provide direct interface
for accessing data form external spi devices.

The one QSPI in the device is primarily intended for fast booting
from Quad SPI flash devices.


MLO/u-boot.img will be flashed from SD/MMC to the flash device
using serial flash erase and write commands. Then, switch settings
will be changed to qspi boot. Then, the ROM code will read MLO
from the predefined location in the flash, where it was flashed and
execute it after storing it in SDRAM. Then, the MLO will read
u-boot.img from flash and execute it from SDRAM.

   - Newly created file which is responsible for configuring the
     qspi controller and also for providing the low level api which
     is responsible for transferring the datas from host controller
     to flash device and vice versa.

A seperated file named README.dra_qspi_test has been created which gives all the
details about the commands required to test qspi at u-boot level.