ipmi: Move the address source to string to ipmi-generic code

It was in the system interface driver, but is generic functionality.

Signed-off-by: Corey Minyard <cminyard@mvista.com>

diff --cc drivers/char/ipmi/ipmi_msghandler.c
Simple merge

diff --cc drivers/char/ipmi/ipmi_si_intf.c
Simple merge

diff --cc include/linux/ipmi.h
Simple merge