ARC: [plat-arcfpga] Fix build breakage when !CONFIG_ARC_SERIAL

This fixes the following:
- CONFIG_ARC_SERIAL_BAUD is only defined when CONFIG_SERIAL_ARC is defined.
  Make sure that it isn't referenced otherwise.
- There is no use for initializing arc_uart_info[] when CONFIG_SERIAL_ARC is
  not defined.

[vgupta: tweaked changelog title, used IS_ENABLED() kconfig helper]
Signed-off-by: Mischa Jonker <mjonker@synopsys.com>
Signed-off-by: Vineet Gupta <vgupta@synopsys.com>

arch/arc/plat-arcfpga/platform.c

@@ -77,6 +77,7 @@ static void __init setup_bvci_lat_unit(void)
 
 /*----------------------- Platform Devices -----------------------------*/
 
+#if IS_ENABLED(CONFIG_SERIAL_ARC)
 static unsigned long arc_uart_info[] = {
 	0,	/* uart->is_emulated (runtime @running_on_hw) */
 	0,	/* uart->port.uartclk */
@@ -115,7 +116,7 @@ static struct platform_device arc_uart0_dev = {
 static struct platform_device *fpga_early_devs[] __initdata = {
 	&arc_uart0_dev,
 };
-#endif
+#endif	/* CONFIG_SERIAL_ARC_CONSOLE */
 
 static void arc_fpga_serial_init(void)
 {
@@ -152,8 +153,13 @@ static void arc_fpga_serial_init(void)
 	 * otherwise the early console never gets a chance to run.
 	 */
 	add_preferred_console("ttyARC", 0, "115200");
-#endif
+#endif	/* CONFIG_SERIAL_ARC_CONSOLE */
+}
+#else	/* !IS_ENABLED(CONFIG_SERIAL_ARC) */
+static void arc_fpga_serial_init(void)
+{
 }
+#endif
 
 static void __init plat_fpga_early_init(void)
 {
@@ -169,7 +175,7 @@ static void __init plat_fpga_early_init(void)
 }
 
 static struct of_dev_auxdata plat_auxdata_lookup[] __initdata = {
-#if defined(CONFIG_SERIAL_ARC) || defined(CONFIG_SERIAL_ARC_MODULE)
+#if IS_ENABLED(CONFIG_SERIAL_ARC)
 	OF_DEV_AUXDATA("snps,arc-uart", UART0_BASE, "arc-uart", arc_uart_info),
 #endif
 	{}