minor cleanup

console.c

@@ -290,7 +290,7 @@ panic(char *s)
   int i;
   uint pcs[10];
   
-  __asm __volatile("cli");
+  cli();
   use_console_lock = 0;
   cprintf("cpu%d: panic: ", cpu());
   cprintf(s);

lapic.c

@@ -97,8 +97,8 @@ cpu(void)
   // Cannot call cpu when interrupts are enabled:
   // result not guaranteed to last long enough to be used!
   // Would prefer to panic but even printing is chancy here:
-  // everything, including cprintf, calls cpu, at least indirectly
-  // through acquire and release.
+  // almost everything, including cprintf and panic, calls cpu,
+  // often indirectly through acquire and release.
   if(read_eflags()&FL_IF){
     static int n;
     if(n++ == 0)