ps2: Add a simple touchscreen model

Add a touchscreen model that is compatible with Linux's TouchKit
driver. This model is based on the model in the Arm PL050 KMI model.

Change-Id: Id4d88a21a26bb42c455e4d778cd89875f650ac57
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/9764
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

ps2: Add VNC support to the keyboard model

Add support for keyboard input from the VNC server in the PS/2
keyboard model. The introduced code is based on the functionality in
the Arm PL050 KMI model.

Change-Id: If04a9713e5a15e2149d1a7471b999e3060d8ee7d
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/9763
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>

ps2: Factor out PS/2 devices into their own subsystem

PS/2 devices are currently emulated both in the i8042 model and the
Arm KMI model. This is undesirable since it leads to code duplication.

This change introduces a common PS/2 device interface and factor out
the x86 keyboard and mouse model. A subsequent commit will implement
support for this interface in the Arm KMI model.

Change-Id: I440e83517fd9dce362fdc1676db477cc6eee5211
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/9762
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Gabe Black <gabeblack@google.com>