boards: Update arc em_starterkit support from 2.2 to 2.3

Here are the main changes:
* board: Update EMSK onboard resources such as Button, Switch and LEDs
  + update soc.h for em7d, em9d, em11d
  + update board.h for em_starterkit board
* arc: Add floating point support and code density support
  + add kconfig configuration
  + add compiler options
  + add register definitions, marcos, assembly codes
  + fixes in existing codes and configurations.
* arc: Update detailed board configurations for cores of emsk 2.3
* script: Provide for debugging em_starterkit board
  + make BOARD=em_starterkit debug
    This will start openocd server for emsk, and arc gdb will connect
    to this debug server, user can run `continue` command if user just
    want to run the application, or other commands if debugging needed.
  + make BOARD=em_starterkit debugserver
    This will start an openocd debugger server for emsk, and user can
    connect to this debugserver using arc gdb and do what they want to.
  + make BOARD=em_starterkit flash
    This will download the zephyr application elf file to emsk,
    and run it.

Signed-off-by: Huaqi Fang <>
26 files changed