labs/debugging-setup: make it clearer that U-Boot command is only one command

Got reported by a future participant, who had written both on the same
line, but without any space, so "...eth0nfsroot". Make it clearer that
there is a space in between, and that those two lines are together by
adding a backslash.

Signed-off-by: Thomas Petazzoni <[email protected]>

Author: tpetazzoni

labs/debugging-setup/debugging-setup.tex

@@ -158,7 +158,7 @@ \section{U-Boot setup}
 and wait for U-Boot prompt to appear. Then, enter the following commands:
 
 \begin{bashinput}
-=> env set bootargs root=/dev/nfs ip=192.168.0.100:::::eth0
+=> env set bootargs root=/dev/nfs ip=192.168.0.100:::::eth0 \
   nfsroot=192.168.0.1:/home/<user>/__SESSION_NAME__-labs/nfsroot/,nfsvers=3,tcp rw
 => saveenv
 \end{bashinput}