Convert CONFIG_VGA_AS_SINGLE_DEVICE to Kconfig

This converts the following to Kconfig:
   CONFIG_VGA_AS_SINGLE_DEVICE

Once we migrate to driver model for video, we should be able to drop this
option.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/conga-qeval20-qa3-e3845-internal-uart_defconfig b/configs/conga-qeval20-qa3-e3845-internal-uart_defconfig
index 6bee9c6..784270c 100644
--- a/configs/conga-qeval20-qa3-e3845-internal-uart_defconfig
+++ b/configs/conga-qeval20-qa3-e3845-internal-uart_defconfig
@@ -65,4 +65,5 @@
 CONFIG_VIDEO_VESA=y
 CONFIG_FRAMEBUFFER_SET_VESA_MODE=y
 CONFIG_FRAMEBUFFER_VESA_MODE_114=y
+CONFIG_CFB_CONSOLE=y
 CONFIG_USE_PRIVATE_LIBGCC=y