Current MMC driver doesn't handle generic error (bit19 of device
status) in write sequence. As a result, write data gets lost when
generic error occurs. For example, a generic error when updating a
filesystem management information causes a loss of write data and
corrupts the filesystem. In the worst case, the system will never
boot.

This patch includes the following functionality:
  1. To enable error checking for the response of CMD12 and CMD13
     in write command sequence
  2. To retry write sequence when a generic error occurs

Messages are added for v2 to show what occurs.
Signed-off-by: KOBAYASHI Yoshitake <yoshitake.kobayashi@toshiba.co.jp>
Signed-off-by: Chris Ball <cjb@laptop.org>