clocksource: hyper-v: Add TSC page support for root partition

Microsoft Hypervisor root partition has to map the TSC page specified
by the hypervisor, instead of providing the page to the hypervisor like
it's done in the guest partitions.

However, it's too early to map the page when the clock is initialized, so, the
actual mapping is happening later.

Signed-off-by: Stanislav Kinsburskiy <stanislav.kinsburskiy@gmail.com>
CC: "K. Y. Srinivasan" <kys@microsoft.com>
CC: Haiyang Zhang <haiyangz@microsoft.com>
CC: Wei Liu <wei.liu@kernel.org>
CC: Dexuan Cui <decui@microsoft.com>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Ingo Molnar <mingo@redhat.com>
CC: Borislav Petkov <bp@alien8.de>
CC: Dave Hansen <dave.hansen@linux.intel.com>
CC: x86@kernel.org
CC: "H. Peter Anvin" <hpa@zytor.com>
CC: Daniel Lezcano <daniel.lezcano@linaro.org>
CC: linux-hyperv@vger.kernel.org
CC: linux-kernel@vger.kernel.org
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Reviewed-by: Anirudh Rayabharam <anrayabh@linux.microsoft.com>
Link: https://lore.kernel.org/r/166759443644.385891.15921594265843430260.stgit@skinsburskii-cloud-desktop.internal.cloudapp.net
Signed-off-by: Wei Liu <wei.liu@kernel.org>

include/clocksource/hyperv_timer.h

@@ -31,6 +31,7 @@ extern void hv_stimer_global_cleanup(void);
 extern void hv_stimer0_isr(void);
 
 extern void hv_init_clocksource(void);
+extern void hv_remap_tsc_clocksource(void);
 
 extern unsigned long hv_get_tsc_pfn(void);
 extern struct ms_hyperv_tsc_page *hv_get_tsc_page(void);