arm: zynq: Move ZYNQ_SERIAL to Kconfig

Move cadence/zynq serial driver via Kconfig

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/xilinx_zynqmp_ep_defconfig b/configs/xilinx_zynqmp_ep_defconfig
index 95665ec..ff865f1 100644
--- a/configs/xilinx_zynqmp_ep_defconfig
+++ b/configs/xilinx_zynqmp_ep_defconfig
@@ -72,6 +72,7 @@
 CONFIG_DEBUG_UART_BASE=0xff000000
 CONFIG_DEBUG_UART_CLOCK=25000000
 CONFIG_DEBUG_UART_ANNOUNCE=y
+CONFIG_ZYNQ_SERIAL=y
 CONFIG_USB=y
 CONFIG_USB_XHCI_HCD=y
 CONFIG_USB_XHCI_DWC3=y