msm: qmi: Fix decoding of multi-level nested structures

As per QMI message wire format, type and length information is added
only for elements in the main/outer structure. For elements within a
nested structure, there is no type and length information.

The kernel encode/decode library skips decoding multi-level
nested structures because of the missing length information.
Calculate the maximum message length of such structures through
their element information and complete the decode operation.

Change-Id: I92ed84d7da888ea6360950c288b7b6df7a79f53b
Signed-off-by: Karthikeyan Ramasubramanian <kramasub@codeaurora.org>