ufs: fixed bugs in ice related to key syncronization

1. Added reference count for requests in HW queue for particular key
2. Fixed race between block/unblock requests with asynchronous job
for key configuration in ice

Change-Id: Iaefc25739b420b2e5feae1895c7c2495b4850539
Signed-off-by: Andrey Markovytch <andreym@codeaurora.org>
[cang@codeaurora.org: dropped changes in pfk_kc.c and
resolved trivial merge conflicts]
Signed-off-by: Can Guo <cang@codeaurora.org>