MAINTAINERS: remove entry after hp100 driver removal

Commit a10079c6

 ("staging: remove hp100 driver") removed all files
from ./drivers/staging/hp/, but missed to adjust MAINTAINERS.

Since then, ./scripts/get_maintainer.pl --self-test=patterns complains:

  warning: no file matches F: drivers/staging/hp/hp100.*

So, drop HP100 Driver entry in MAINTAINERS now.

Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Link: https://lore.kernel.org/r/20200429042116.29126-1-lukas.bulwahn@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>