input: synaptics: add NULL pointer check

Add null pointer exception check for pointers which
may be NULL after memory allocation failure and
may be deferenced.

This patch is propagated from msm-3.10 kernel
(commit: 66af29b24da01340efc511e8d63b33c04ebe5273
input: synaptics: add NULL pointer check)
Also cleaned checkpatch warning on msm-3.18 kernel.

Change-Id: I99a24ada5b91743bc57568b6ab7b39e655c7bb64
Signed-off-by: Sarada Prasanna Garnayak <c_sgarna@codeaurora.org>
Signed-off-by: Sudhakar Manapati <smanap@codeaurora.org>