disk/part.c: fix potential stack overflow bug

If the param pass to get_dev is not the one defined in the block_drvr,
it could make uboot becomes unstable, for it would continue run after
search complete the block_drvr table.
Signed-off-by: NLei Wen <leiwen@marvell.com>

disk/part.c

@@ -84,7 +84,7 @@ block_dev_desc_t *get_dev(char* ifname, int dev)
 #ifdef CONFIG_NEEDS_MANUAL_RELOC
 	name += gd->reloc_off;
 #endif
-	while (name) {
+	while (drvr->name) {
 		name = drvr->name;
 		reloc_get_dev = drvr->get_dev;
 #ifdef CONFIG_NEEDS_MANUAL_RELOC