configs/beaglebone_defconfig: use default console device

OMAP kernels use 8250 driver by default. Hence the name of
the console device is not /dev/ttyO0 but /dev/ttyS0.
Use /dev/console in order to handle the console independently
of the selected driver.

Tested in BeagleBone Black board.

Signed-off-by: Yegor Yefremov <yegorslists@googlemail.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
(cherry picked from commit 68b5b79b2fb316fd7c6c40c12a7e9ddaeada837d)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

configs/beaglebone_defconfig

@@ -2,7 +2,6 @@ BR2_arm=y
 BR2_cortex_a8=y
 BR2_GLOBAL_PATCH_DIR="board/beaglebone/patches"
 BR2_PACKAGE_HOST_LINUX_HEADERS_CUSTOM_4_14=y
-BR2_TARGET_GENERIC_GETTY_PORT="ttyO0"
 BR2_ROOTFS_POST_IMAGE_SCRIPT="board/beaglebone/post-image.sh"
 BR2_LINUX_KERNEL=y
 BR2_LINUX_KERNEL_CUSTOM_GIT=y