staging: kpc2000: use kzalloc(sizeof(var)...) in cell_probe.c

Fixes checkpatch.pl warning "Prefer kzalloc(sizeof(*kudev)...) over
kzalloc(sizeof(struct kpc_uio_device)...)"

Signed-off-by: Simon Sandström <simon@nikanor.nu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>