hw/arm: sabrelite: Connect the Ethernet PHY at address 6

hw/arm: sabrelite: Connect the Ethernet PHY at address 6

At present, when booting U-Boot on QEMU sabrelite, we see:

  Net:   Board Net Initialization Failed
  No ethernet found.

U-Boot scans PHY at address 4/5/6/7 (see board_eth_init() in the
U-Boot source: board/boundary/nitrogen6x/nitrogen6x.c). On the real
board, the Ethernet PHY is at address 6. Adjust this by updating the
"fec-phy-num" property of the fsl_imx6 SoC object.

With this change, U-Boot sees the PHY but complains MAC address:

  Net:   using phy at 6
  FEC [PRIME]
  Error: FEC address not set.

This is due to U-Boot tries to read the MAC address from the fuse,
which QEMU does not have any valid content filled in. However this
does not prevent the Ethernet from working in QEMU. We just need to
set up the MAC address later in the U-Boot command shell, by:

  => setenv ethaddr 00:11:22:33:44:55

Signed-off-by: Bin Meng <bin.meng@windriver.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Message-id: 20210106063504.10841-4-bmeng.cn@gmail.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>