Add a cpu_throw() function that secondary CPU's can use for their first

context switch.

sys/alpha/alpha/swtch.s

@@ -86,6 +86,16 @@ Lsavectx1: LDGP(pv)
 
 IMPORT(Lev1map, 8)
 
+/*
+ * cpu_throw()
+ * Switch to a new task discarding our current state.
+ */
+LEAF(cpu_throw, 0)
+	LDGP(pv)
+	mov	zero, s0			/* ensure newproc != oldproc */
+	CALL(Lcs1)
+	END(cpu_throw)
+
 /*
  * cpu_switch()
  * Find the highest priority process and resume it.