[arch][x86] add missing pv.h file added a few commits back

arch/x86/include/arch/x86/pv.h

@@ -0,0 +1,19 @@
+/*
+ * Copyright (c) 2025 Travis Geiselbrecht
+ *
+ * Use of this source code is governed by a MIT-style
+ * license that can be found in the LICENSE file or at
+ * https://opensource.org/licenses/MIT
+ */
+#pragma once
+
+#include <sys/types.h>
+#include <stdbool.h>
+
+#if !X86_LEGACY
+
+status_t pvclock_init(void);
+uint64_t pvclock_get_tsc_freq(void);
+bool pv_clock_is_stable(void);
+
+#endif // !X86_LEGACY