Staging: kpc2000: Cleanup in kpc_dma_transfer()

Remove unnecessary typecast in kzalloc function. In addition to that
replace kzalloc(sizeof(*acd)) over kzalloc(sizeof(struct aio_cb_data))
to maintain Linux kernel style.

Issue suggested by Coccinelle.

Signed-off-by: Madhumitha Prabakaran <madhumithabiw@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>