mmc: core: Cleanup code for setting ocr mask for SDIO

At several places in mmc_sdio_init_card function the cached mask in
host->ocr were being updated. To simplify code, we make use of an
local ocr parameter instead.

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Chris Ball <cjb@laptop.org>