dt-bindings: input: iqs5xx: Convert to YAML

dt-bindings: input: iqs5xx: Convert to YAML

This patch converts the legacy text-based binding document to YAML
format. Extraneous details and touchscreen properties that weren't
actually supported have been dropped.

The reset GPIO has since been made optional in the driver; this is
now reflected here as well.

Signed-off-by: Jeff LaBundy <jeff@labundy.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20210323021006.367-2-jeff@labundy.com
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>