HID: uhid: Remove the redundant reference counting for open/close

Currently, the uhid driver manages the reference count for the number
of clients active for this uhid device. However, the reference count
is already managed by the hid-core. As a result, during uhid_open for
example, we never get the UHID_OPEN event in the upper layers as the
reference count is incremented twice for each open(). Hence, let the
reference counting be done only by the hid-core and not by the uhid
driver.

Change-Id: I473239db0f373d9188fc379653cedd305d2a552b
Signed-off-by: Raghavendra Rao Ananta <rananta@codeaurora.org>