Disable kernel preemption, fix requesting rescheduling

kernel/amd64/smp.h

@@ -2,6 +2,7 @@
 #define _KERNEL_AMD64_SMP_H
 
 #include <amd64/gdt.h>
+#include <amd64/intr.h>
 #include <amd64/tss.h>
 #include <aux/compiler.h>
 #include <libk/rbtree.h>
@@ -20,6 +21,7 @@ struct cpu {
   volatile uint8_t irq_stack[KSTACK_SIZE] ALIGNED (16);
   volatile struct gdt_extended gdt ALIGNED (16);
   volatile struct tss tss;
+  struct saved_regs regs;
 
   uintptr_t lapic_mmio_base;
   uint64_t lapic_ticks;