boards: spresense: Add CONFIG_BOARD_LATE_INITIALIZE=y for SMP

Summary:
- I noticed that spresense:rndis_smp and spresense:wifi_smp
  do not boot due to the recent change in nx_start.c
- As the result of the discussion, I understand that we have to
  add CONFIG_BOARD_LATE_INITIALIZE=y for SMP

Impact:
- spresense only

Testing:
- Tested with spresense:rndis_smp and spresense:wifi_smp

Signed-off-by: Masayuki Ishikawa <masayuki.ishikawa@gmail.com>

boards/arm/cxd56xx/spresense/configs/rndis_smp/defconfig

@@ -22,6 +22,7 @@ CONFIG_AUDIO=y
 CONFIG_AUDIO_CXD56=y
 CONFIG_BOARDCTL_RESET=y
 CONFIG_BOARDCTL_USBDEVCTRL=y
+CONFIG_BOARD_LATE_INITIALIZE=y
 CONFIG_BOARD_LOOPSPERMSEC=5434
 CONFIG_BOOT_RUNFROMISRAM=y
 CONFIG_BUILTIN=y

boards/arm/cxd56xx/spresense/configs/smp/defconfig

@@ -14,6 +14,7 @@ CONFIG_ARCH_CHIP="cxd56xx"
 CONFIG_ARCH_CHIP_CXD56XX=y
 CONFIG_ARCH_STACKDUMP=y
 CONFIG_ARMV7M_USEBASEPRI=y
+CONFIG_BOARD_LATE_INITIALIZE=y
 CONFIG_BOARD_LOOPSPERMSEC=5434
 CONFIG_BOOT_RUNFROMISRAM=y
 CONFIG_BUILTIN=y

boards/arm/cxd56xx/spresense/configs/wifi_smp/defconfig

@@ -22,6 +22,7 @@ CONFIG_ARMV7M_USEBASEPRI=y
 CONFIG_AUDIO=y
 CONFIG_AUDIO_CXD56=y
 CONFIG_BOARDCTL_RESET=y
+CONFIG_BOARD_LATE_INITIALIZE=y
 CONFIG_BOARD_LOOPSPERMSEC=5434
 CONFIG_BOOT_RUNFROMISRAM=y
 CONFIG_BUILTIN=y

boards/arm/cxd56xx/spresense/src/cxd56_appinit.c

@@ -77,3 +77,28 @@ int board_app_initialize(uintptr_t arg)
   return cxd56_bringup();
 #endif
 }
+
+/****************************************************************************
+ * Name: board_late_initialize
+ *
+ * Description:
+ *   If CONFIG_BOARD_LATE_INITIALIZE is selected, then an additional
+ *   initialization call will be performed in the boot-up sequence to a
+ *   function called board_late_initialize().  board_late_initialize()
+ *   will be called immediately after up_initialize() is called and just
+ *   before the initial application is started.  This additional
+ *   initialization phase may be used, for example, to initialize board-
+ *   specific device drivers.
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_BOARD_LATE_INITIALIZE
+void board_late_initialize(void)
+{
+  /* Perform board bring-up here instead of from the
+   * board_app_initialize().
+   */
+
+  cxd56_bringup();
+}
+#endif