staging/ft1000: use kzalloc to allocate the ft1000_device structure

with kzalloc the allocate memory is set to zero, so no need of
calling memset again on the allocated memory

Signed-off-by: Devendra Naga <devendra.aaru@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>