mmc: cqhci: add CQHCI_SSC1 register CBC field mask

This patch adds define for CBC field mask of the register
CQHCI_SSC1.

Tested-by: Jon Hunter <jonathanh@nvidia.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Sowjanya Komatineni <skomatineni@nvidia.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>