When running a simple GUI it is useful to support a mouse. This is
similar to what is provided in UEFI's boot menu. Add a simple uclass and
a way to read the mouse position.
For sandbox add a driver that reads the position from SDL. Disable input
for the tools-only build, since it is of no use there and causes build
failures.
Signed-off-by: Simon Glass <sjg@chromium.org>
74cf6bee6c