crypto: msm: Fix key length setting

Hardcoding key length to a constant value results in overwriting
command element information in the command descriptor beyond what
is allocate for the key information in the command element list.
This results in corruption of the command list in the case where
command descriptors are used for configuring crypto registers and
needlessly writing to key registers that are not relevant to the
operation (when writing to registers directly), and thus leads to
crypto operation failures. Fix is to use the key length based on
what is requested by the client.

Change-Id: Ibd625dc7a438fac84b13588700bf472004e246d5
Signed-off-by: Zhen Kong <zkong@codeaurora.org>