HID: hid-picolcd_core: Remove unused variable 'ret'

Fixes the following W=1 kernel build warning(s):

 drivers/hid/hid-picolcd_core.c: In function ‘picolcd_raw_event’:
 drivers/hid/hid-picolcd_core.c:332:6: warning: variable ‘ret’ set but not used [-Wunused-but-set-variable]

Cc: "Bruno Prémont" <bonbons@linux-vserver.org>
Cc: Jiri Kosina <jikos@kernel.org>
Cc: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Cc: "L. Vinyard, Jr" <rvinyard@cs.nmsu.edu>
Cc: linux-input@vger.kernel.org
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>