Staging: ti-st: fix protocol counting

Older mechanism of counting the number of protocols
registered with ST was slow, in-efficient.
It used to check the protocol data for NULL for each
registration/unregistration.

With this change, counting protocols in maintained by
a single counter protos_registered.

Counting protocols is not just for debug purposes

Signed-off-by: Naveen Jain <naveen_jain@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>