platform: msm: remove usage of __devexit_p in 3.18 kernel

__devexit_p is deprecated in 3.18 kernel. Hence, remove the
usage of __devexit_p from the vibrator driver.

Change-Id: I334652ea2d73d80e59a1dca5db11cd25484210b4
Signed-off-by: Abinaya P <abinayap@codeaurora.org>