arch: cxd56xx: Do not re-initialize the console for subcore

If the subcore configuration, which is mainly used in the Spresense
Arduino environment, is enabled, the serial console has been already
initialized by maincore. Then, don't need to re-initialize the UART1
serial driver.

arch/arm/src/cxd56xx/cxd56_serial.c

@@ -460,6 +460,17 @@ static int up_setup(FAR struct uart_dev_s *dev)
   uint32_t lcr;
   uint32_t cr;
 
+#ifdef CONFIG_CXD56_SUBCORE
+  if (priv->id == 1)
+    {
+      /* In case of SUBCORE, UART1 has been already initialized,
+       * then we don't need to do anything.
+       */
+
+      return OK;
+    }
+#endif
+
   cxd56_uart_setup(priv->id);
 
   /* Init HW */

arch/arm/src/cxd56xx/cxd56_start.c

@@ -303,7 +303,9 @@ void __start(void)
 
   putreg32(0, CXD56_EXCCONF_BASE + 0);
 
+#ifndef CONFIG_CXD56_SUBCORE
   cxd56_lowsetup();
+#endif
   showprogress('A');
 
   /* Clear .bss.  We'll do this inline (vs. calling memset) just to be
@@ -327,7 +329,7 @@ void __start(void)
 
   /* Perform early serial initialization */
 
-#ifdef USE_EARLYSERIALINIT
+#if defined(USE_EARLYSERIALINIT) && !defined(CONFIG_CXD56_SUBCORE)
   arm_earlyserialinit();
 #endif
   showprogress('E');