x86: shift bits the right way in native_read_tscp

native_read_tscp shifts the bits in the high order value in the
wrong direction, the attached patch fixes that.

Signed-off-by: Max Asbock <masbock@linux.vnet.ibm.com>
Acked-by: Glauber Costa <gcosta@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>