roms/u-boot-sam460ex: Change to qemu git mirror and update

Now that we have a mirror of this repo on git.qemu.org change the
submodule to use that and update it to latest commit which fixes a
dangling symlink and removes two big binaries that are not needed.

Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

.gitmodules

@@ -45,4 +45,4 @@
 	url = git://github.com/hdeller/seabios-hppa.git
 [submodule "roms/u-boot-sam460ex"]
 	path = roms/u-boot-sam460ex
-	url = git://github.com/zbalaton/u-boot-sam460ex
+	url = git://git.qemu.org/u-boot-sam460ex.git

roms/u-boot-sam460ex

@@ -1 +1 @@
-Subproject commit 119aa277f74a4a2d3f7ab6c9471292308eba14e4
+Subproject commit 8ee007c4216fd6a0d760589e8405ce4494497aa0