ev3: add "console=tty1" to bootscript

Unfortunaly, this is done mainly to work around issues with hardware
UARTS on EV3 that we can't figure out.

The side effect is that console messages will print on the screen during
boot, which can be useful for troubleshooting.

Issue: ev3dev/ev3dev#623

bootscript/bootscr.ev3

@@ -1,3 +1,3 @@
 run loadimage
-setenv bootargs mem=${memsize} console=${console} root=/dev/mmcblk0p2 rw rootwait splash @@LINUX_KERNEL_CMDLINE@@
+setenv bootargs mem=${memsize} console=${console} console=tty1 root=/dev/mmcblk0p2 rw rootwait splash @@LINUX_KERNEL_CMDLINE@@
 bootm ${loadaddr}