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/T1040RDB_SECURE_BOOT_defconfig b/configs/T1040RDB_SECURE_BOOT_defconfig
index 6d61ab5..7b19069 100644
--- a/configs/T1040RDB_SECURE_BOOT_defconfig
+++ b/configs/T1040RDB_SECURE_BOOT_defconfig
@@ -3,6 +3,7 @@
 CONFIG_TARGET_T104XRDB=y
 CONFIG_SYS_EXTRA_OPTIONS="PPC_T1040,SECURE_BOOT,T1040RDB"
 CONFIG_SPI_FLASH=y
+CONFIG_SPI_FLASH_STMICRO=y
 CONFIG_NETDEVICES=y
 CONFIG_E1000=y
 CONFIG_SYS_NS16550=y