Revert "Remove unused define"

This reverts commit edf2c6cf5adc82ee43c81e033cf2215eb9ffdb16.
diff --git a/arch/arch-alpha.h b/arch/arch-alpha.h
index e204368..a5e3801 100644
--- a/arch/arch-alpha.h
+++ b/arch/arch-alpha.h
@@ -51,4 +51,6 @@
 	lock->lock = 0;
 }
 
+#define __SPIN_LOCK_UNLOCKED	{ 0 }
+
 #endif
diff --git a/arch/arch-ia64.h b/arch/arch-ia64.h
index 37284b1..d9afc32 100644
--- a/arch/arch-ia64.h
+++ b/arch/arch-ia64.h
@@ -67,4 +67,6 @@
 	__asm__ __volatile__("st4.rel.nta [%0] = r0\n\t" :: "r" (lock));
 }
 
+#define __SPIN_LOCK_UNLOCKED	{ 0 }
+
 #endif
diff --git a/arch/arch-x86.h b/arch/arch-x86.h
index 51d7d96..b9249ea 100644
--- a/arch/arch-x86.h
+++ b/arch/arch-x86.h
@@ -69,4 +69,6 @@
 			: "memory", "cc");
 }
 
+#define __SPIN_LOCK_UNLOCKED	{ 0 }
+
 #endif
diff --git a/arch/arch-x86_64.h b/arch/arch-x86_64.h
index c8c3d18..71ba224 100644
--- a/arch/arch-x86_64.h
+++ b/arch/arch-x86_64.h
@@ -69,4 +69,6 @@
 			: "memory", "cc");
 }
 
+#define __SPIN_LOCK_UNLOCKED	{ 0 }
+
 #endif