arch: arm: Add support for the Nordic nRF52840 IC

The new Nordic nRF52840 IC is the latest member of the nRF52 family.
It supports the following features among others:

    * Cortex-M4F core at 64MHz
    * 1024KB of flash and 256KB of RAM
    * Bluetooth 5-ready and 802.15.4 compatible radio
    * USB device support
    * NFC Tag support
    * Quad-SPI
    * Hardware accelerated crypto engine

http://www.nordicsemi.com/eng/Products/nRF52840



JIRA: ZEP-1418

Change-Id: I677c787bb33d02695e057d5dced7e3455b9f6c50
Signed-off-by: Vinayak Chettimada <vinayak.kariappa.chettimada@nordicsemi.no>
Signed-off-by: Carles Cufi <carles.cufi@nordicsemi.no>