x86/paravirt: Add _safe to the read_ms()r and write_msr() PV callbacks

These callbacks match the _safe variants, so name them accordingly.
This will make room for unsafe PV callbacks.

Tested-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Andy Lutomirski <luto@kernel.org>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: KVM list <kvm@vger.kernel.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: xen-devel <Xen-devel@lists.xen.org>
Link: http://lkml.kernel.org/r/9ee3fb6a196a514c93325bdfa15594beecf04876.1459605520.git.luto@kernel.org


Signed-off-by: Ingo Molnar <mingo@kernel.org>