Embedded Linux: fix STM32 U-Boot instructions

They were still refering to the Ethernet ports on SAMA5D3 Xplained

Signed-off-by: Michael Opdenacker <michael.opdenacker@bootlin.com>

labs/sysdev-u-boot-stm32/sysdev-u-boot-stm32.tex

@@ -306,7 +306,7 @@ \section{Setting up Ethernet communication}
 To start with, install and configure a TFTP server on your development
 workstation, as detailed in the bootloader slides.
 
-With a network cable, connect the Ethernet port labelled ETH0/GETH of
+With a network cable, connect the Ethernet port of
 your board to the one of your computer. If your computer already has a
 wired connection to the network, your instructor will provide you with
 a USB Ethernet adapter. A new network interface should appear on your