Kernel: Use a constexpr declaration for the disabled PIC IRQ base

Author: https://github.com/supercomputer7
Commit: 7028a64997
Pull-request: https://github.com/SerenityOS/serenity/pull/12182
Issue: https://github.com/SerenityOS/serenity/issues/12134
Reviewed-by: https://github.com/IdanHo ✅
Reviewed-by: https://github.com/Panky-codes

Kernel/Interrupts/PIC.h

@@ -10,6 +10,9 @@
 #include <Kernel/Interrupts/IRQController.h>
 
 namespace Kernel {
+
+static constexpr size_t pic_disabled_vector_base = 0x20;
+
 class PIC final : public IRQController {
 public:
     PIC();