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/db-mv784mp-gp_defconfig b/configs/db-mv784mp-gp_defconfig
index 054c71d..4c4329d 100644
--- a/configs/db-mv784mp-gp_defconfig
+++ b/configs/db-mv784mp-gp_defconfig
@@ -9,6 +9,8 @@
 # CONFIG_CMD_SETEXPR is not set
 CONFIG_NAND_PXA3XX=y
 CONFIG_SPI_FLASH=y
+CONFIG_SPI_FLASH_MACRONIX=y
+CONFIG_SPI_FLASH_STMICRO=y
 CONFIG_SYS_NS16550=y
 CONFIG_USB=y
 CONFIG_DM_USB=y