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/M54455EVB_a66_defconfig b/configs/M54455EVB_a66_defconfig
index e82d0bd..e810273 100644
--- a/configs/M54455EVB_a66_defconfig
+++ b/configs/M54455EVB_a66_defconfig
@@ -5,3 +5,4 @@
 # CONFIG_CMD_LOADS is not set
 # CONFIG_CMD_SETEXPR is not set
 CONFIG_SPI_FLASH=y
+CONFIG_SPI_FLASH_STMICRO=y