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>

include/linux/ipmi.h

@@ -278,6 +278,7 @@ enum ipmi_addr_src {
 	SI_INVALID = 0, SI_HOTMOD, SI_HARDCODED, SI_SPMI, SI_ACPI, SI_SMBIOS,
 	SI_PCI,	SI_DEVICETREE, SI_DEFAULT
 };
+const char *ipmi_addr_src_to_str(enum ipmi_addr_src src);
 
 union ipmi_smi_info_union {
 	/*