clocksource/drivers/hyper-v: Handle vDSO differences inline

clocksource/drivers/hyper-v: Handle vDSO differences inline

While the driver for the Hyper-V Reference TSC and STIMERs is architecture
neutral, vDSO is implemented for x86/x64, but not for ARM64.  Current code
calls into utility functions under arch/x86 (and coming, under arch/arm64)
to handle the difference.

Change this approach to handle the difference inline based on whether
VDSO_CLOCK_MODE_HVCLOCK is present.  The new approach removes code under
arch/* since the difference is tied more to the specifics of the Linux
implementation than to the architecture.

No functional change.

Signed-off-by: Michael Kelley <mikelley@microsoft.com>
Reviewed-by: Boqun Feng <boqun.feng@gmail.com>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/1614721102-2241-8-git-send-email-mikelley@microsoft.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>