Input: optimize events_per_packet count calculation

This patch avoids unnecessary operations while estimating events per
packet for an input device when event type is not set.

Change-Id: I913be1e5356d5ca7d3047e6b0413069993c2921c
Signed-off-by: Anshul Garg <anshul.g@samsung.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Git-commit: baf332c0f1cede26e9c2af6276b36b4c3a36e34a
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git


Signed-off-by: Matt Wagantall <mattw@codeaurora.org>