arm: imx6: tqma6: boot device selection via Kconfig

Signed-off-by: Markus Niebel <Markus.Niebel@tq-group.com>
diff --git a/configs/tqma6q_mba6_spi_defconfig b/configs/tqma6q_mba6_spi_defconfig
index bba751c..f8a44bf 100644
--- a/configs/tqma6q_mba6_spi_defconfig
+++ b/configs/tqma6q_mba6_spi_defconfig
@@ -1,6 +1,7 @@
 CONFIG_ARM=y
 CONFIG_ARCH_MX6=y
 CONFIG_TARGET_TQMA6=y
-CONFIG_SYS_EXTRA_OPTIONS="MBA6,TQMA6X_SPI_BOOT"
+CONFIG_TQMA6X_SPI_BOOT=y
+CONFIG_SYS_EXTRA_OPTIONS="MBA6"
 CONFIG_CMD_SETEXPR=y
 CONFIG_CMD_NET=y