core/console: use char literals instead of numeric
core/console: use char literals instead of numeric

Save everyone a trip to asciitable.com. I realise everyone has probably
memorised \n and friends, but THAT'S NOT THE POINT.

Signed-off-by: Oliver O'Halloran <3dfaff8fa6ae977f042064a112a6aac576279b9b@gmail.com>
Reviewed-by: Andrew Donnellan <efc2d7c347a094a6ec1d918179e819039044c564@au1.ibm.com>
Signed-off-by: Stewart Smith <ec31ab75ddf977353c8f660f92ea8b23f64aef25@linux.vnet.ibm.com>

legoater/skiboot,shenki/skiboot,shenki/skiboot,stewart-ibm/skiboot,open-power/skiboot,mikey/skiboot,qemu/skiboot,qemu/skiboot,open-power/skiboot,shenki/skiboot,legoater/skiboot,mikey/skiboot,stewart-ibm/skiboot,qemu/skiboot,legoater/skiboot,qemu/skiboot,legoater/skiboot,open-power/skiboot,open-power/skiboot,open-power/skiboot,shenki/skiboot,shenki/skiboot,mikey/skiboot,qemu/skiboot,legoater/skiboot,stewart-ibm/skiboot