parport: Remove 'drivers' list

The list has been empty since:
 'commit 3275158f ("parport: remove use of devmodel")'

This also means we can remove the 'list_head' from
struct parport_driver.

Signed-off-by: Dr. David Alan Gilbert <linux@treblig.org>
Acked-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
Link: https://lore.kernel.org/r/20240502154823.67235-2-linux@treblig.org


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