serial: uartlite: Move driver to DM

Enable SPL DM too.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Thomas Chou <thomas@wytron.com.tw>
diff --git a/arch/microblaze/Kconfig b/arch/microblaze/Kconfig
index 604f681..30ea484 100644
--- a/arch/microblaze/Kconfig
+++ b/arch/microblaze/Kconfig
@@ -13,6 +13,7 @@
 	select SUPPORT_SPL
 	select OF_CONTROL
 	select DM
+	select DM_SERIAL
 
 endchoice