msm: qpnp-haptic: cancel polling timer before starting a new timer

To handle concurrent requests, cancel the previous instance of the
polling timer just before starting a new instance of the same timer
in order to avoid concurrent access to hrtimer apis.

Change-Id: Ia424da65288666857d6f99d4b543a99434536396
Signed-off-by: Abinaya P <abinayap@codeaurora.org>