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/net2big_v2_defconfig b/configs/net2big_v2_defconfig
index 9f52638..87f4f92 100644
--- a/configs/net2big_v2_defconfig
+++ b/configs/net2big_v2_defconfig
@@ -6,4 +6,5 @@
 # CONFIG_CMD_FLASH is not set
 # CONFIG_CMD_SETEXPR is not set
 CONFIG_SPI_FLASH=y
+CONFIG_SPI_FLASH_MACRONIX=y
 CONFIG_SYS_NS16550=y