sparc: Kconfig: Move the CMD_AMBAPP command to Kconfig

Add an initr function in the board_r.c file for the AMBA Plug&Play
command. Add a Kconfig entry for the ambapp command and remove all
CONFIG_CMD_AMBAPP defines from the board configuration headers.

Add a Kconfig entry to display the AMBA Plug&Play information
on startup. This option is off by default. Remove relevent define
from board configuration headers.

Signed-off-by: Francois Retief <fgretief@spaceteq.co.za>