sdmmc: don’t flip word order in MMC_RSP_BITS

sdmmc: don’t flip word order in MMC_RSP_BITS

MMC_RSP_BITS helper function had a hack that it flipped word order in
the response, assuming that response size is 4 words. This hack does not
work for responses which are not 4 words long (such as the SWITCH_FUNC
response, which is 64 words long).

This change removes the hack and the matching word order reversal code
in sdmmc driver.