BugLink: http://bugs.launchpad.net/bugs/1676635

Make the MSR and TSC clock sources available during the hv_init() and
export them via hyperv_cs in a similar way as the following upstream
commit does:

commit dee863b5 ("hv: export current Hyper-V clocksource")
Signed-off-by: Marcelo Henrique Cerri <marcelo.cerri@canonical.com>
Acked-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
Acked-by: Andy Whitcroft <apw@canonical.com>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>