mx6sxsabresd: Load the correct dtb for revA board

Currently only imx6sx-sdb.dtb is loaded, but if revA board is used the
correct dtb is imx6sx-sdb-reva.dtb, so make this possible.

While at it, remove an extra 'mmc dev'.

Signed-off-by: Fabio Estevam <fabio.estevam@nxp.com>
diff --git a/arch/arm/mach-imx/mx6/Kconfig b/arch/arm/mach-imx/mx6/Kconfig
index bee7eab..44d2db4 100644
--- a/arch/arm/mach-imx/mx6/Kconfig
+++ b/arch/arm/mach-imx/mx6/Kconfig
@@ -255,6 +255,7 @@
 
 config TARGET_MX6SXSABRESD
 	bool "mx6sxsabresd"
+	select BOARD_LATE_INIT
 	select MX6SX
 	select SUPPORT_SPL
 	select DM