Clean up AHCI: volatile, and sata_reset

src/kernel/io.h

@@ -25,7 +25,8 @@ uint64_t rdmsr(uint64_t addr);
 void wrmsr(uint64_t addr, uint64_t value);
 
 /// Pause briefly by doing IO to port 0x80
-void io_wait();
+/// \arg times  Number of times to delay by writing
+void io_wait(unsigned times = 1);
 
 }