ssb: remove the ssb DMA API

Now they are unnecessary.  We can use the generic DMA API with any bus.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: Michael Buesch <mb@bu3sch.de>
Cc: Gary Zambrano <zambrano@broadcom.com>
Cc: Stefano Brivio <stefano.brivio@polimi.it>
Cc: Larry Finger <Larry.Finger@lwfinger.net>
Cc: John W. Linville <linville@tuxdriver.com>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>