Convert CONSOLE_PRE_CONSOLE_BUFFER options to Kconfig

Move these option to Kconfig and tidy up existing uses.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Jagan Teki <jteki@openedev.com>
diff --git a/configs/tbs2910_defconfig b/configs/tbs2910_defconfig
index fbff9fe..0871408 100644
--- a/configs/tbs2910_defconfig
+++ b/configs/tbs2910_defconfig
@@ -1,6 +1,8 @@
 CONFIG_ARM=y
 CONFIG_ARCH_MX6=y
 CONFIG_TARGET_TBS2910=y
+CONFIG_PRE_CONSOLE_BUFFER=y
+CONFIG_PRE_CON_BUF_ADDR=0x7c000000
 CONFIG_FIT=y
 CONFIG_BOOTDELAY=3
 CONFIG_HUSH_PARSER=y