x86: kconfig: Let board select SPI flash

Only a specific type of SPI flash exists on a board, having board
Kconfig to select the SPI flash seems to make more sense. Other
flash types are not necessary except coreboot, which implies all
available flash drivers there.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/board/google/chromebox_panther/Kconfig b/board/google/chromebox_panther/Kconfig
index 2af3aa9..875df9d 100644
--- a/board/google/chromebox_panther/Kconfig
+++ b/board/google/chromebox_panther/Kconfig
@@ -22,6 +22,7 @@
 	select NORTHBRIDGE_INTEL_IVYBRIDGE
 	select HAVE_INTEL_ME
 	select BOARD_ROMSIZE_KB_8192
+	select SPI_FLASH_WINBOND
 
 config SYS_CAR_ADDR
 	hex