hw/ppc/sam460ex: Update u-boot-sam460ex

hw/ppc/sam460ex: Update u-boot-sam460ex

Update the sam460ex firmware to match 2015.c version from the machine
vendor which fixes USB devices and some other bugs. Also cherry pick
some commits from upstream U-Boot that moves licenses in a subdir and
allows gitlab to correctly detect and show license information. Drop
version number from the binary name to avoid needing to change it in
case of future updates.

Signed-off-by: BALATON Zoltan <balaton@eik.bme.hu>
Message-Id: <20251028151923.10DBB5972E5@zero.eik.bme.hu>
Signed-off-by: Harsh Prateek Bora <harshpb@linux.ibm.com>