cmd: sbi: Correctly display unknown implementation IDs

For an unknown implementation ID an output like

    SBI 1.0Unknown implementation ID 16777216
    Extensions:
      sbi_set_timer
      ...

was shown. The number 16777216 is not the implementation ID.

* Show the correct number
* Use a hexadecimal output format
* Add a missing line feed

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Dan Carpenter <dan.carpenter@linaro.org>