ipmi_si: fix memory leak on new_smi

The error exit path omits kfree'ing the allocated new_smi, causing a memory
leak.  Fix this by kfree'ing new_smi.

Detected by CoverityScan, CID#14582571 ("Resource Leak")

Fixes: 7e030d6dff71 ("ipmi: Prefer ACPI system interfaces over SMBIOS ones")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Corey Minyard <cminyard@mvista.com>

drivers/char/ipmi/ipmi_si_intf.c

@@ -2004,6 +2004,7 @@ int ipmi_si_add_smi(struct si_sm_io *io)
 				 ipmi_addr_src_to_str(new_smi->io.addr_source),
 				 si_to_str[new_smi->io.si_type]);
 			rv = -EBUSY;
+			kfree(new_smi);
 			goto out_err;
 		}
 	}