drivers: mmc: sysfs interface to Enable / Disable CRC

 * ***** SysFs interface :
 *
 * /sys/module/mmc_core/parameters/crc
 *
 * Enable / Disable CRC
 *
 * echo N > /sys/module/mmc_core/parameters/crc (Disabled) or
 * echo 0 > /sys/module/mmc_core/parameters/crc (Disabled)
 *
 * echo Y > /sys/module/mmc_core/parameters/crc (Enlabled) or
 * echo 1 > /sys/module/mmc_core/parameters/crc (Enabled)
 *
 *
 * ***** (default = Disabled)