msm: kgsl: Don't unregister input handler on removing device

Previous commit has already removed the registering of this
input handler, so do not unregister it.

This will help prevent something unstable from happening.

Fixes: b9993ac603a3 (msm: kgsl: Don't wake up GPU on input events)
Signed-off-by: Wang Han <416810799@qq.com>