staging: unisys: visornic: fixed a typo cant -> can't

Fixed a typo: cant -> can't in visornic_main.c.

Signed-off-by: Liu Junqi <liujunqi@pku.edu.cn>
Link: https://lore.kernel.org/r/20211125044729.594727-1-liujunqi@pku.edu.cn


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>