Input: olpc_apsp - remove set but not used variable 'np'

Fixes gcc '-Wunused-but-set-variable' warning:

drivers/input/serio/olpc_apsp.c: In function 'olpc_apsp_probe':
drivers/input/serio/olpc_apsp.c:192:22: warning:
 variable 'np' set but not used [-Wunused-but-set-variable]

It never used since introduction in commit b56ece9a ("Input: add OLPC
AP-SP driver")

Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Acked-by: Lubomir Rintel <lkundrak@v3.sk>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>