x86, uv: Remove recursion in uv_heartbeat_enable()

The recursion is not needed and does not improve readability.

Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
LKML-Reference: <4B45F13E.3040202@gmail.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>