parport: cleanup statics initialization to NULL or 0

based on checkpatch, cleanup the "do not initialise statics to" 0 or NULL.

Signed-off-by: Carlos Palminha <palminha@synopsys.com>
Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>