Remove the dma mask parsing from dt as this should not be encoded into
the engine device tree node. Keep the fallback value for now, which
should work for the boards already supported upstream.

Signed-off-by: Antoine Tenart <antoine.tenart@free-electrons.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>