arm: zynq: Move serial driver to driver model

Update this driver to use driver model and change all users.

Signed-off-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>
diff --git a/arch/arm/Kconfig b/arch/arm/Kconfig
index fa51d62..0d756cb 100644
--- a/arch/arm/Kconfig
+++ b/arch/arm/Kconfig
@@ -547,6 +547,7 @@
 	select DM
 	select SPL_DM
 	select DM_SPI
+	select DM_SERIAL
 	select DM_SPI_FLASH
 	select SPL_SEPARATE_BSS