xtensa: provide dummy gcc intrinsics

__xtensa_libgcc_window_spill is needed for __builtin_return_address(1),
but its libgcc implementation cannot be used as it makes a syscall.

Atomic intrinsics are used by single staging driver.

Signed-off-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Chris Zankel <chris@zankel.net>

arch/xtensa/kernel/xtensa_ksyms.c

@@ -74,8 +74,25 @@ EXPORT_SYMBOL(__umodsi3);
 EXPORT_SYMBOL(__udivdi3);
 EXPORT_SYMBOL(__umoddi3);
 EXPORT_SYMBOL(__ucmpdi2);
+
+void __xtensa_libgcc_window_spill(void)
+{
+	BUG();
+}
 EXPORT_SYMBOL(__xtensa_libgcc_window_spill);
 
+unsigned long __sync_fetch_and_and_4(unsigned long *p, unsigned long v)
+{
+	BUG();
+}
+EXPORT_SYMBOL(__sync_fetch_and_and_4);
+
+unsigned long __sync_fetch_and_or_4(unsigned long *p, unsigned long v)
+{
+	BUG();
+}
+EXPORT_SYMBOL(__sync_fetch_and_or_4);
+
 #ifdef CONFIG_NET
 /*
  * Networking support