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/chromebook_samus_defconfig b/configs/chromebook_samus_defconfig
index 4f8d9fa..f19d861 100644
--- a/configs/chromebook_samus_defconfig
+++ b/configs/chromebook_samus_defconfig
@@ -59,5 +59,6 @@
 CONFIG_FRAMEBUFFER_SET_VESA_MODE=y
 CONFIG_FRAMEBUFFER_VESA_MODE_11A=y
 CONFIG_VIDEO_BROADWELL_IGD=y
+CONFIG_CONSOLE_SCROLL_LINES=5
 CONFIG_USE_PRIVATE_LIBGCC=y
 CONFIG_TPM=y