board/qemu/ppc64le-pseries: put Qemu command on one line

This allows the toolchain building machinery used by
https://toolchains.bootlin.com to automatically re-use this Qemu
command line.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

board/qemu/ppc64le-pseries/readme.txt

@@ -1,8 +1,6 @@
 Run the emulation with:
 
-qemu-system-ppc64 -M pseries -nographic \
-		-kernel output/images/vmlinux \
-		-initrd output/images/rootfs.ext2
+qemu-system-ppc64 -M pseries -nographic -kernel output/images/vmlinux -initrd output/images/rootfs.ext2
 
 The login prompt will appear in the terminal window.