HID: logitech: fix a used uninitialized GCC warning
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;