ps2: Initial horizontal scroll support

This change adds support for horizontal scroll to ps/2 mouse device
code. The code is implemented to match the logic of linux kernel
which is used as a reference.

Signed-off-by: Dmitry Petrov <dpetroff@gmail.com>
Message-Id: <20220108153947.171861-2-dpetroff@gmail.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>