sf: Move SPI flash drivers to defconfig

There are already Kconfig options for SPI flash drivers, but we
have not moved them from config.h to defconfig files. This commit
does this in a batch.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/configs/BSC9132QDS_SPIFLASH_DDRCLK100_defconfig b/configs/BSC9132QDS_SPIFLASH_DDRCLK100_defconfig
index 5436458..a1a5cd3 100644
--- a/configs/BSC9132QDS_SPIFLASH_DDRCLK100_defconfig
+++ b/configs/BSC9132QDS_SPIFLASH_DDRCLK100_defconfig
@@ -3,6 +3,7 @@
 CONFIG_TARGET_BSC9132QDS=y
 CONFIG_SYS_EXTRA_OPTIONS="BSC9132QDS,SPIFLASH,SYS_CLK_100_DDR_100"
 CONFIG_SPI_FLASH=y
+CONFIG_SPI_FLASH_SPANSION=y
 CONFIG_NETDEVICES=y
 CONFIG_E1000=y
 CONFIG_SYS_NS16550=y