mmc: core: Reduce code duplication to mmc_spi_send_{csd|cid}

mmc_spi_send_{csd|cid} have similar function body. Let's remove the
duplicated part to simplify the code, just add opcode to distinguish
them in changed mmc_spi_send_cxd().

Signed-off-by: Yue Hu <huyue2@yulong.com>
Link: https://lore.kernel.org/r/20210215015116.1355-1-zbestahu@gmail.com


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