serial: samsung: Add support for early console

This patch adds support for early console initialized from device tree
and kernel command line to all variants of Samsung serial driver.

Signed-off-by: Tomasz Figa <t.figa@samsung.com>
[mszyprow: added support for command line based initialization,
           fixed comments, added documentation]
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Alim Akhtar <alim.akhtar@samsung.com>
Tested-by: Alim Akhtar <alim.akhtar@samsung.com>
Tested-by: Chanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/tty/serial/Kconfig b/drivers/tty/serial/Kconfig
index 35677f7..c63317e 100644
--- a/drivers/tty/serial/Kconfig
+++ b/drivers/tty/serial/Kconfig
@@ -241,6 +241,7 @@
 	tristate "Samsung SoC serial support"
 	depends on PLAT_SAMSUNG || ARCH_EXYNOS
 	select SERIAL_CORE
+	select SERIAL_EARLYCON
 	help
 	  Support for the on-chip UARTs on the Samsung S3C24XX series CPUs,
 	  providing /dev/ttySAC0, 1 and 2 (note, some machines may not