staging: csr: remove driver

This driver is not being updated as the specifications are not able to
be gotten from CSR or anyone else.  Without those, getting this driver
into proper mergable shape is going to be impossible.  So remove the
driver from the tree.

If the specifications ever become available, this patch can be reverted
and the driver fixed up properly.

Reported-by: Lidza Louina <lidza.louina@gmail.com>
Cc: Veli-Pekka Peltola <veli-pekka.peltola@bluegiga.com>
Cc: Mikko Virkkilä <mikko.virkkila@bluegiga.com>
Cc: Lauri Hintsala <Lauri.Hintsala@bluegiga.com>
Cc: Riku Mettälä <riku.mettala@bluegiga.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>