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/P1010RDB-PB_36BIT_SDCARD_defconfig b/configs/P1010RDB-PB_36BIT_SDCARD_defconfig
index 6447053..ac6ee07 100644
--- a/configs/P1010RDB-PB_36BIT_SDCARD_defconfig
+++ b/configs/P1010RDB-PB_36BIT_SDCARD_defconfig
@@ -4,6 +4,7 @@
 CONFIG_SPL=y
 CONFIG_SYS_EXTRA_OPTIONS="P1010RDB_PB,36BIT,SDCARD"
 CONFIG_SPI_FLASH=y
+CONFIG_SPI_FLASH_SPANSION=y
 CONFIG_NETDEVICES=y
 CONFIG_E1000=y
 CONFIG_SYS_NS16550=y