Convert CONFIG_CONSOLE_SCROLL_LINES to Kconfig

This converts the following to Kconfig:
   CONFIG_CONSOLE_SCROLL_LINES

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/conga-qeval20-qa3-e3845_defconfig b/configs/conga-qeval20-qa3-e3845_defconfig
index b5ef570..45220bc 100644
--- a/configs/conga-qeval20-qa3-e3845_defconfig
+++ b/configs/conga-qeval20-qa3-e3845_defconfig
@@ -65,4 +65,5 @@
 CONFIG_FRAMEBUFFER_SET_VESA_MODE=y
 CONFIG_FRAMEBUFFER_VESA_MODE_114=y
 CONFIG_CFB_CONSOLE=y
+CONFIG_CONSOLE_SCROLL_LINES=5
 CONFIG_USE_PRIVATE_LIBGCC=y