spi: armada-3700: Remove unnecessary condition

We checked that "a3700_spi->wait_mask & cause" was set at the beginning
of the function so we don't need to check again here.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Romain Perier <romain.perier@free-electrons.com>
Signed-off-by: Mark Brown <broonie@kernel.org>