[TF-A] Addition of write() capability to IO MTD layer

Hello,

A project I’m working on requires write capability for a NOR flash device in BL2 (to update a small boot mux partition). I am considering adding this capability to the IO MTD layer (https://github.com/ARM-software/arm-trusted-firmware/blob/master/drivers/io/...), but before doing so wanted to confirm this is in line with the architecture of this subsystem. Can someone confirm if this is an acceptable change?

Regards, Brian