Blackfin arch: early prink code still use uart core console functions to parse and set configure option string

Signed-off-by: Sonic Zhang <sonic.zhang@analog.com>
Signed-off-by: Bryan Wu <cooloney@kernel.org>

diff --git a/arch/blackfin/Kconfig.debug b/arch/blackfin/Kconfig.debug
index 2cb0a30..f08aea4 100644
--- a/arch/blackfin/Kconfig.debug
+++ b/arch/blackfin/Kconfig.debug
@@ -184,6 +184,7 @@
 config EARLY_PRINTK
 	bool "Early printk" 
 	default n
+	select SERIAL_CORE_CONSOLE
 	help
 	  This option enables special console drivers which allow the kernel
 	  to print messages very early in the bootup process.