Use generic spin () instead of amd64_spin ()

kernel/amd64/hpet.c

@@ -4,6 +4,7 @@
 #include <sync/spin_lock.h>
 #include <sys/debug.h>
 #include <sys/mm.h>
+#include <sys/spin.h>
 #include <uacpi/acpi.h>
 #include <uacpi/status.h>
 #include <uacpi/tables.h>
@@ -32,10 +33,6 @@ static uint64_t hpet_clock_nano;
 /// Lock, which protects concurrent access. See \ref amd64/smp.c
 static spin_lock_t hpet_lock = SPIN_LOCK_INIT;
 
-/** @cond DOXYGEN_IGNORE */
-extern void amd64_spin (void);
-/** @endcond */
-
 /// Read a HPET register. Assumes caller holds \ref hpet_lock
 static uint64_t amd64_hpet_read (uint32_t reg) {
   struct limine_hhdm_response* hhdm = limine_hhdm_request.response;
@@ -93,7 +90,7 @@ void amd64_hpet_init (void) {
   uacpi_status status = uacpi_table_find_by_signature (ACPI_HPET_SIGNATURE, &hpet_table);
   if (status != UACPI_STATUS_OK) {
     DEBUG ("Could not find HPET table!\n");
-    amd64_spin ();
+    spin ();
   }
 
   struct acpi_hpet* hpet = (struct acpi_hpet*)hpet_table.virt_addr;