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_NAND_defconfig b/configs/T1040RDB_NAND_defconfig
index 93fd9d9..74f22d2 100644
--- a/configs/T1040RDB_NAND_defconfig
+++ b/configs/T1040RDB_NAND_defconfig
@@ -4,6 +4,7 @@
 CONFIG_SPL=y
 CONFIG_SYS_EXTRA_OPTIONS="PPC_T1040,T1040RDB,RAMBOOT_PBL,SPL_FSL_PBL,NAND"
 CONFIG_SPI_FLASH=y
+CONFIG_SPI_FLASH_STMICRO=y
 CONFIG_NETDEVICES=y
 CONFIG_E1000=y
 CONFIG_SYS_NS16550=y