Input: silead - Always support 10 fingers

When support for Silead touchscreens was orginal added some touchscreens
with older firmware versions only supported 5 fingers and this was made
the default requiring the setting of a "silead,max-fingers=10" uint32
device-property for all touchscreen models which do support 10 fingers.

There are very few models with the old 5 finger fw, so in practice the
setting of the "silead,max-fingers=10" is boilerplate which needs to
be copy and pasted to every touchscreen config.

Reporting that 10 fingers are supported on devices which only support
5 fingers doesn't cause any problems for userspace in practice, since
at max 4 finger gestures are supported anyways. Drop the max_fingers
configuration and simply always assume 10 fingers.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Link: https://lore.kernel.org/r/20240525193854.39130-2-hdegoede@redhat.com