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/sandbox_defconfig b/configs/sandbox_defconfig
index 0178674..c4e1be3 100644
--- a/configs/sandbox_defconfig
+++ b/configs/sandbox_defconfig
@@ -39,6 +39,14 @@
 CONFIG_DM_MMC=y
 CONFIG_SPI_FLASH_SANDBOX=y
 CONFIG_SPI_FLASH=y
+CONFIG_SPI_FLASH_ATMEL=y
+CONFIG_SPI_FLASH_EON=y
+CONFIG_SPI_FLASH_GIGADEVICE=y
+CONFIG_SPI_FLASH_MACRONIX=y
+CONFIG_SPI_FLASH_SPANSION=y
+CONFIG_SPI_FLASH_STMICRO=y
+CONFIG_SPI_FLASH_SST=y
+CONFIG_SPI_FLASH_WINBOND=y
 CONFIG_DM_ETH=y
 CONFIG_DM_PCI=y
 CONFIG_PCI_SANDBOX=y