The drivers using the type B protocol all report tracking information
the same way. The contact id is semantically equivalent to
ABS_MT_SLOT, and the handling of ABS_MT_TRACKING_ID only complicates
the driver. The situation can be improved upon by providing a common
pointer emulation code, thereby removing the need for the tracking id
in the driver.  This patch moves all tracking event handling over to
the input core, simplifying both the existing drivers and the ones
currently in preparation.
Acked-by: NPing Cheng <pingc@wacom.com>
Acked-by: NJiri Kosina <jkosina@suse.cz>
Signed-off-by: NHenrik Rydberg <rydberg@euromail.se>

The MT slots devices all follow the same initialization pattern
of creating slots and hinting about buffer size. Let drivers call
an initialization function instead, and make sure it can be called
repeatedly without side effects.
Signed-off-by: NHenrik Rydberg <rydberg@euromail.se>

In preparation for common code to handle a larger set of MT slots
devices, move the slots handling over to a separate file.
Signed-off-by: NHenrik Rydberg <rydberg@euromail.se>