part: check each variable for capability calculation

In order to calculate the capability, we use the below expression to check:
((dev_desc->lba * dev_desc->blksz)>0L)
If the capability is greater than 4GB (e.g. 8GB = 8 * 1024 * 104 * 1024),
the result will overflow, the low 32bit may be zero.

Therefore, change to check each variable to fix this potential issue.
Signed-off-by: NJerry Huang <Chang-Ming.Huang@freescale.com>

disk/part.c

@@ -199,7 +199,7 @@ void dev_print (block_dev_desc_t *dev_desc)
 		break;
 	}
 	puts ("\n");
-	if ((dev_desc->lba * dev_desc->blksz)>0L) {
+	if (dev_desc->lba > 0L && dev_desc->blksz > 0L) {
 		ulong mb, mb_quot, mb_rem, gb, gb_quot, gb_rem;
 		lbaint_t lba;