Remove unused nop_pause function.

runoff

@@ -192,6 +192,8 @@ do
 	if [ "x$defs" != "x$uses" ]; then
 		echo $i $defs
 		echo $uses |fmt -29 | sed 's/^/    /'
+#	else
+#		echo $i defined but not used >&2
 	fi
 done
 ) >refs

x86.h

@@ -137,12 +137,6 @@ xchg(volatile uint *addr, uint newval)
   return result;
 }
 
-static inline void
-nop_pause(void)
-{
-  asm volatile("pause" : :);
-}
-
 //PAGEBREAK!
 static inline void
 lcr0(uint val)