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/T1040D4RDB_defconfig b/configs/T1040D4RDB_defconfig
index c28afab..6feecb3 100644
--- a/configs/T1040D4RDB_defconfig
+++ b/configs/T1040D4RDB_defconfig
@@ -3,6 +3,7 @@
 CONFIG_TARGET_T104XRDB=y
 CONFIG_SYS_EXTRA_OPTIONS="PPC_T1040,T1040D4RDB,T104XD4RDB,SYS_FSL_DDR4"
 CONFIG_SPI_FLASH=y
+CONFIG_SPI_FLASH_STMICRO=y
 CONFIG_NETDEVICES=y
 CONFIG_E1000=y
 CONFIG_SYS_NS16550=y