mmc: cqhci: fix space allocated for transfer descriptor

There is not enough space being allocated when DCMD is disabled.

CQE_DCMD is not necessary to be enabled when CQE is enabled.
(Software could halt CQE to send command)

In the case that CQE_DCMD is not enabled, it still needs to allocate
space for data transfer. For instance:
  CQE_DCMD is enabled:  31 slots space (one slot used by DCMD)
  CQE_DCMD is disabled: 32 slots space

Fixes: a4080225 ("mmc: cqhci: support for command queue enabled host")
Signed-off-by: Alamy Liu <alamy.liu@gmail.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: stable@vger.kernel.org
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>