spmi: msm: correct len part in formatted cmd value.

When the bytes count required by SPMI clients is 8, read and write
fail. This was observed when PMIC MPPs initialized. Fix this by
adding bytes count restore in cmd formation as read and write process.

Change-Id: I56dbbc0b8e99727c29ddae568ce6f17195888b4a
Signed-off-by: Yimin Peng <yiminp@codeaurora.org>