x86: Kconfig: Move DM_SPI & DM_SPI_FLASH to arch/Kconfig

Since all x86 boards have been converted to use DM_SPI and
DM_SPI_FLASH, move them to arch/Kconfig x86 section.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Acked-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/Kconfig b/arch/Kconfig
index 1102346..200588a 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -93,6 +93,8 @@
 	select DM
 	select DM_SERIAL
 	select DM_GPIO
+	select DM_SPI
+	select DM_SPI_FLASH
 
 endchoice