hv/mod_timer: make timer into an arch-independent module

x86/timer.[ch] was moved to the common directory largely unchanged.

x86 specific code now resides in x86/tsc_deadline_timer.c and its
interface was defined in hw/hw_timer.h. The interface defines two
functions: init_hw_timer() and set_hw_timeout() that provides HW
specific initialization and timer interrupt source.

Other than these two functions, the timer module is largely arch
agnostic.

Tracked-On: #5920
Signed-off-by: Rong Liu <rong2.liu@intel.com>
Reviewed-by: Jason Chen CJ <jason.cj.chen@intel.com>

hypervisor/include/hw/hw_timer.h

@@ -0,0 +1,15 @@
+/*
+ * Copyright (C) 2021 Intel Corporation.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#ifndef HW_TIMER_H
+#define HW_TIMER_H
+
+#include <types.h>
+
+void set_hw_timeout(uint64_t timeout);
+void init_hw_timer(void);
+
+#endif