IPMI: fix comparison in demangle_device_id

Coverity spotted some incorrect code in a recent change to the IPMI driver;
this patch make sure the data is really long enough to pull the
manufacturer id and product id out of a get device id message.
Signed-off-by: Corey Minyard <cminyard@mvista.com>
Cc: Adrian Bunk <bunk@kernel.org>
Cc: Stian Jordet <liste@jordet.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/ipmi_smi.h

@@ -173,7 +173,7 @@ static inline int ipmi_demangle_device_id(const unsigned char *data,
 	id->firmware_revision_2 = data[3];
 	id->ipmi_version = data[4];
 	id->additional_device_support = data[5];
-	if (data_len >= 6) {
+	if (data_len >= 11) {
 		id->manufacturer_id = (data[6] | (data[7] << 8) |
 				       (data[8] << 16));
 		id->product_id = data[9] | (data[10] << 8);