[U-Boot] Patch: Fix device enumeration through API.

[Tim Kientzle]

The one-line patch below fixes device enumeration through the
U-Boot API.

Device enumeration crashes when the system in question doesn't
have any RAM mapped to address zero (I discovered this on a
BeagleBone board), since the enumeration calls get_dev with a
NULL ifname sometimes which then gets passed down to strncmp().

This fix simply ensures that get_dev returns NULL when invoked
with a NULL ifname.

This could also be fixed by reworking the device enumeration to
never call get_dev with a NULL argument, but that's a much more
extensive change.  (get_dev is called from several places and the
code is driven by a list that's constructed in a way that naturally
leaves lots of NULLs.)

Cheers,

Tim Kientzle

diff --git a/disk/part.c b/disk/part.c
index f07a17f..1a82539 100644
--- a/disk/part.c
+++ b/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 (drvr->name) {
+	while (ifname && drvr->name) {
 		name = drvr->name;
 		reloc_get_dev = drvr->get_dev;
 #ifdef CONFIG_NEEDS_MANUAL_RELOC