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/zynq_zybo_defconfig b/configs/zynq_zybo_defconfig
index d0ef223..4126460 100644
--- a/configs/zynq_zybo_defconfig
+++ b/configs/zynq_zybo_defconfig
@@ -51,6 +51,7 @@
 CONFIG_DEBUG_UART_ZYNQ=y
 CONFIG_DEBUG_UART_BASE=0xe0001000
 CONFIG_DEBUG_UART_CLOCK=50000000
+CONFIG_ZYNQ_SERIAL=y
 CONFIG_ZYNQ_QSPI=y
 CONFIG_USB=y
 CONFIG_USB_EHCI_HCD=y