x86, uv, uv3: Update Time Support for SGI UV3

This patch updates time support for the SGI UV3 hub.  Since the UV2
and UV3 time support is identical, "is_uvx_hub" is used instead of
having both "is_uv2_hub" and "is_uv3_hub".

Signed-off-by: Mike Travis <travis@sgi.com>
Link: http://lkml.kernel.org/r/20130211194508.893907185@gulag1.americas.sgi.com
Acked-by: Russ Anderson <rja@sgi.com>
Reviewed-by: Dimitri Sivanich <sivanich@sgi.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>