Documentation: platform: Delete x86-laptop-drivers.txt

The list of laptops supported by drivers in PDx86 subsystem is quite
big and growing. x86-laptop-drivers.txt contains details of very few
laptop models. Remove it because it does not  serve any purpose.

Signed-off-by: Puranjay Mohan <puranjay12@gmail.com>
Acked-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>