mmc: use max_discard_to for SD write timeout

mmc: use max_discard_to for SD write timeout

BZ: 24030

max_discard_to is the max timeout value allowed by host. Use
this value can stop kernel printing too large timeout warning.

Change-Id: Iaa0828475849f466f45ef55d3d4c8ae7f220b073
Signed-off-by: Chuanxiao Dong <chuanxiao.dong@intel.com>
Reviewed-on: http://android.intel.com:8080/35692
Reviewed-by: Gross, Mark <mark.gross@intel.com>
Tested-by: Sun, Jianhua <jianhua.sun@intel.com>
Reviewed-by: Tang, Richard <richard.tang@intel.com>
Reviewed-by: buildbot <buildbot@intel.com>
Tested-by: buildbot <buildbot@intel.com>