Use RW spin locks

kernel/amd64/smp.h

@@ -7,6 +7,7 @@
 #include <libk/rbtree.h>
 #include <libk/std.h>
 #include <proc/proc.h>
+#include <sync/rw_spin_lock.h>
 
 #define CPUS_MAX 32
 
@@ -29,7 +30,7 @@ struct cpu {
     atomic_int nesting;
   } irq_ctx;
 
-  spin_lock_t lock;
+  rw_spin_lock_t lock;
 
   struct rb_node_link* proc_run_q;
   struct proc* proc_current;