configs/liteboard: remove explicit getty port

Using default value (console) works well, so there is no reason to set
tty explicitly.

Signed-off-by: Marcin Niestroj <m.niestroj@grinn-global.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

configs/grinn_liteboard_defconfig

@@ -1,7 +1,6 @@
 BR2_arm=y
 BR2_cortex_a7=y
 BR2_PACKAGE_HOST_LINUX_HEADERS_CUSTOM_4_16=y
-BR2_TARGET_GENERIC_GETTY_PORT="ttymxc0"
 BR2_SYSTEM_DHCP="eth0"
 BR2_ROOTFS_POST_IMAGE_SCRIPT="board/grinn/liteboard/post-image.sh"
 BR2_LINUX_KERNEL=y