dt-bindings: crypto: remove mediatek ethif clock

This patch removes the parent clock 'ethif' in bindings, since we don't
need to control the parent of a clock in current clock framework.

Moreover, the clocks are get by name in the driver, thus this change
does not break backwards compatibility.

Signed-off-by: Ryder Lee <ryder.lee@mediatek.com>
Reviewed-by: Matthias Brugger <matthias.bgg@gmail.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>