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/smdk5420_defconfig b/configs/smdk5420_defconfig
index c7cbbbb..50148fc 100644
--- a/configs/smdk5420_defconfig
+++ b/configs/smdk5420_defconfig
@@ -10,6 +10,8 @@
 # CONFIG_CMD_SETEXPR is not set
 CONFIG_DM_I2C_COMPAT=y
 CONFIG_SPI_FLASH=y
+CONFIG_SPI_FLASH_GIGADEVICE=y
+CONFIG_SPI_FLASH_WINBOND=y
 CONFIG_DM_PMIC=y
 CONFIG_DM_REGULATOR=y
 CONFIG_EXYNOS_SPI=y