[kernel] Create system_map_mmio syscall

Create a syscall for drivers to be able to ask the kernel for a VMA that
maps a MMIO area. Also expose vm_flags via j6 table style include file
and new flags.h header.

src/include/j6/flags.h

@@ -0,0 +1,10 @@
+#pragma once
+/// \file flags.h
+/// Enums used as flags for syscalls
+
+enum j6_vm_flags {
+#define VM_FLAG(name, v) j6_vm_flag_ ## name = v,
+#include "j6/tables/vm_flags.inc"
+#undef VM_FLAG
+	j6_vm_flags_MAX
+};