[PATCH] libata-eh-fw: add flags and operations for new EH

Add ATA_FLAG_EH_{PENDING|FROZEN}, ATA_ATA_QCFLAG_{FAILED|SENSE_VALID}
and ops->freeze, thaw, error_handler, post_internal_cmd() for new EH.

Signed-off-by: Tejun Heo <htejun@gmail.com>