mmc: mmci: Fix typo in comment

Delete the redundant word 'is'.

Signed-off-by: Xiang wangx <wangxiang@cdjrlc.com>
Link: https://lore.kernel.org/r/20220608130847.46359-1-wangxiang@cdjrlc.com


Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>