tmscsim: replace by am53c974 driver

The am53c974 is a re-implementation of the tmscsim driver,
and provides the same functionality.
So remove the tmscsim driver and make am53c974 an alias to tmscsim.

Acked-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>