ipmi:dmi: Ignore IPMI SMBIOS entries with a zero base address

Looking at logs from systems all over the place, it looks like tons
of broken systems exist that set the base address to zero.  I can
only guess that is some sort of non-standard idea to mark the
interface as not being present.  It can't be zero, anyway, so just
complain and ignore it.
Signed-off-by: Corey Minyard <cminyard@mvista.com>

drivers/char/ipmi/ipmi_dmi.c

@@ -218,6 +218,10 @@ static void __init dmi_decode_ipmi(const struct dmi_header *dm)
 	slave_addr = data[DMI_IPMI_SLAVEADDR];
 
 	memcpy(&base_addr, data + DMI_IPMI_ADDR, sizeof(unsigned long));
+	if (!base_addr) {
+		pr_err("Base address is zero, assuming no IPMI interface\n");
+		return;
+	}
 	if (len >= DMI_IPMI_VER2_LENGTH) {
 		if (type == IPMI_DMI_TYPE_SSIF) {
 			offset = 0;