serial: zynq: Fix incorrect reference to s5p driver

Remove this c&p error from s5p driver.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/serial/Kconfig b/drivers/serial/Kconfig
index 82ad90d..1fc287e 100644
--- a/drivers/serial/Kconfig
+++ b/drivers/serial/Kconfig
@@ -95,7 +95,7 @@
 config DEBUG_UART_ZYNQ
 	bool "Xilinx Zynq"
 	help
-	  Select this to enable a debug UART using the serial_s5p driver. You
+	  Select this to enable a debug UART using the serial_zynq driver. You
 	  will need to provide parameters to make this work. The driver will
 	  be available until the real driver-model serial is running.