x86, uv: fix compile error in uv_hub.h

Impact: include file dependency cleanup

Fix compile errors of files that include asm/uv/uv_hub.h but do
not include linux/timer.h.

[ such files are not mainline right now. ]

Signed-of-by: Mike Travis <travis@sgi.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>