x86/time: use correct guest TSC frequency in tsc_get_info()

x86/time: use correct guest TSC frequency in tsc_get_info()

When the TSC mode of a HVM container is TSC_MODE_DEFAULT or
TSC_MODE_PVRDTSCP and no TSC emulation is used, the existing
tsc_get_info() uses the host TSC frequency (cpu_khz) as the guest TSC
frequency. However, tsc_set_info() may set the guest TSC frequency to a
value different than the host. In order to keep consistent to
tsc_set_info(), this patch makes tsc_get_info() use the value set by
tsc_set_info() as the guest TSC frequency.

Signed-off-by: Haozhong Zhang <haozhong.zhang@intel.com>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>