Fix the following compile warning:

drivers/hid/hid-logitech-hidpp.c: In function 'hi_res_scroll_enable':
drivers/hid/hid-logitech-hidpp.c:2714:54: warning: 'multiplier' may be used uninitialized in this function [-Wmaybe-uninitialized]
  hidpp->vertical_wheel_counter.resolution_multiplier = multiplier;
Signed-off-by: zhong jiang <zhongjiang@huawei.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>