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_SPIFLASH_defconfig b/configs/T1040RDB_SPIFLASH_defconfig
index c58ddc2..3305e49 100644
--- a/configs/T1040RDB_SPIFLASH_defconfig
+++ b/configs/T1040RDB_SPIFLASH_defconfig
@@ -4,6 +4,7 @@
 CONFIG_SPL=y
 CONFIG_SYS_EXTRA_OPTIONS="PPC_T1040,T1040RDB,RAMBOOT_PBL,SPL_FSL_PBL,SPIFLASH"
 CONFIG_SPI_FLASH=y
+CONFIG_SPI_FLASH_STMICRO=y
 CONFIG_NETDEVICES=y
 CONFIG_E1000=y
 CONFIG_SYS_NS16550=y