msm: kgsl: Add function stubs for CONFIG_INPUT not set

The input handler code needs CONFIG_INPUT to be set. In the event
that the config is not set, the compiler complains and so add
ifdefs based on CONFIG_INPUT set.

Change-Id: I36ddad9a1ff7c4d6fb900ec7190bd6ef853a62c8
Signed-off-by: Shrenuj Bansal <shrenujb@codeaurora.org>