feat: further kernel power and power optimizations

kernel/src/Drivers/USB/Xhci.hpp

@@ -110,6 +110,7 @@ namespace Drivers::USB::Xhci {
     // IMAN bits
     constexpr uint32_t IMAN_IP         = (1 << 0);   // Interrupt Pending
     constexpr uint32_t IMAN_IE         = (1 << 1);   // Interrupt Enable
+    constexpr uint32_t IMOD_INTERVAL_100US = 400;    // 100 us in 250 ns units
 
     // ---------------------------------------------------------------------------
     // TRB (Transfer Request Block) - 16 bytes