staging: nvec: check return value

In nvec_kbd_probe(), the return value of devm_input_allocate_device()
should be checked before it is used.

Signed-off-by: Xidong Wang <wangxidong_97@163.com>
Link: https://lore.kernel.org/r/1576648598-12257-1-git-send-email-wangxidong_97@163.com


Acked-by: Marc Dietrich <marvin24@gmx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>