Init error to 0 for sdmmc_mem_single_{read,write}_block otherwise the value would be uninitialised in the unlikely case of being called with length 0.
Init error to 0 for sdmmc_mem_single_{read,write}_block
otherwise the value would be uninitialised in the unlikely
case of being called with length 0.

orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars,orumin/openbsd-efivars