mmc: core: Remove unused macro mmc_req_rel_wr

There is no user for macro mmc_req_rel_wr, so delete it.

Signed-off-by: Bean Huo <beanhuo@micron.com>
Link: https://lore.kernel.org/r/20230403221754.16168-1-beanhuo@iokpp.de


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