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/P1010RDB-PA_SPIFLASH_SECBOOT_defconfig b/configs/P1010RDB-PA_SPIFLASH_SECBOOT_defconfig
index 280a638..751cc54 100644
--- a/configs/P1010RDB-PA_SPIFLASH_SECBOOT_defconfig
+++ b/configs/P1010RDB-PA_SPIFLASH_SECBOOT_defconfig
@@ -3,6 +3,7 @@
 CONFIG_TARGET_P1010RDB=y
 CONFIG_SYS_EXTRA_OPTIONS="P1010RDB_PA,SPIFLASH,SECURE_BOOT"
 CONFIG_SPI_FLASH=y
+CONFIG_SPI_FLASH_SPANSION=y
 CONFIG_NETDEVICES=y
 CONFIG_E1000=y
 CONFIG_SYS_NS16550=y