add iotdk flash driver support

[vonhust]

Could you add the iotdk flash driver support into openocd?

So users can download their program into iotdk's flash through gdb and openocd

Iotdk has two flashs supporting XIP
* internal eflash
* external bootspi flash.

There are already some simple drivers in embarc_osp for reference.
https://github.com/foss-for-synopsys-dwc-arc-processors/embarc_osp/tree/master/board/iotdk/drivers/smic

[ruuddw]

See zephyrproject-rtos/zephyr#15793 for a user requesting this.

[abrodkin]

@ruuddw @vonhust @nashif how urgent is this one? Is it blocking any Zephyr release activities?

[ruuddw]

It's not blocking a release, and there's other ways of using the board for developement.
But, it would be good to support the 'standard' way of working for this board instead of only downloading to ICCM/DCCM with the debugger.

[anthony-kolesov]

Note that there is a frawework for flash support in https://github.com/foss-for-synopsys-dwc-arc-processors/openocd/tree/master/src/flash/nand