arch: xtensa: Fix the PS register handling

Summary:
- I noticed that DEBUGASSERT sometimes happens in nxsem_wait()
  when testing Wi-Fi with esp32-devkitc:wsifi_smp
- The call stack was not from an interrupt handler and actually
  g_current_regs[] were correct, even though asserted with
  (up_interrupt_handler() == false)
- Finally, I found that we need to call rsync after we set
  a new value to the PS register which is described in the
  Xtensa document.
- This commit fixes this issue

Impact:
- All xtensa architectures

Testing:
- Tested with esp32-devkitc:wifi_smp and esp32-devkitc:wifi

Signed-off-by: Masayuki Ishikawa <Masayuki.Ishikawa@jp.sony.com>

arch/xtensa/include/irq.h

@@ -203,7 +203,11 @@ static inline void xtensa_setps(uint32_t ps)
 {
   __asm__ __volatile__
   (
-    "wsr %0, PS"  : : "r"(ps)
+    "wsr %0, PS \n"
+    "rsync \n"
+    :
+    : "r"(ps)
+    : "memory"
   );
 }
 
@@ -213,7 +217,11 @@ static inline void up_irq_restore(uint32_t ps)
 {
   __asm__ __volatile__
   (
-    "wsr %0, PS"  : : "r"(ps)
+    "wsr %0, PS \n"
+    "rsync \n"
+    :
+    : "r"(ps)
+    : "memory"
   );
 }