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/chromebox_panther_defconfig b/configs/chromebox_panther_defconfig
index 7ce29fb..23609e0 100644
--- a/configs/chromebox_panther_defconfig
+++ b/configs/chromebox_panther_defconfig
@@ -53,5 +53,6 @@
 CONFIG_FRAMEBUFFER_SET_VESA_MODE=y
 CONFIG_FRAMEBUFFER_VESA_MODE_11A=y
 CONFIG_CFB_CONSOLE=y
+CONFIG_CONSOLE_SCROLL_LINES=5
 CONFIG_USE_PRIVATE_LIBGCC=y
 CONFIG_TPM=y