mmc: Avoid extra duplicate entry in mmc device structure

mmc: Avoid extra duplicate entry in mmc device structure

The 'op_cond_response' field in mmc structure contains the response
from the last SEND_OP_COND MMC command while making iterational
polling of the card. Later it is copied to 'ocr' field, designed
to contain the OCR register value, which is actually the same
response from the same command. So, these fields have actually
the same data, just in different time periods. It's easier to use
the same 'ocr' field in both cases at once, without temporary using
of the 'op_cond_response' field.

Signed-off-by: Andrew Gabbasov <andrew_gabbasov@mentor.com>