bios_emulator: Add Kconfig and adjust Makefile for SPL

The Kconfig for this is currently inside a particular board. Move it into
the correct place and allow use in SPL, so that video can be used there
if needed.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/drivers/bios_emulator/Kconfig b/drivers/bios_emulator/Kconfig
new file mode 100644
index 0000000..3660576
--- /dev/null
+++ b/drivers/bios_emulator/Kconfig
@@ -0,0 +1,10 @@
+config BIOSEMU
+	bool
+	select X86EMU_RAW_IO
+
+config SPL_BIOSEMU
+	bool
+	select X86EMU_RAW_IO
+
+config X86EMU_RAW_IO
+	bool