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/P3041DS_SPIFLASH_defconfig b/configs/P3041DS_SPIFLASH_defconfig
index 12303d1..2c52861 100644
--- a/configs/P3041DS_SPIFLASH_defconfig
+++ b/configs/P3041DS_SPIFLASH_defconfig
@@ -3,6 +3,7 @@
 CONFIG_TARGET_P3041DS=y
 CONFIG_SYS_EXTRA_OPTIONS="RAMBOOT_PBL,SPIFLASH,SYS_TEXT_BASE=0xFFF40000"
 CONFIG_SPI_FLASH=y
+CONFIG_SPI_FLASH_SPANSION=y
 CONFIG_NETDEVICES=y
 CONFIG_E1000=y
 CONFIG_SYS_NS16550=y