soc: qcom: smd-rpm: Correct size of outgoing message

With the removal of VLAIS the size was incorrectly changed to only cover
the headers of the packet, resulting in "empty" requests being sent to
the RPM. Correct this so the entire message is transfered.

Fixes: 50e1b29b ("soc: qcom: smd: Remove use of VLAIS")
Signed-off-by: Bjorn Andersson <bjorn.andersson@sonymobile.com>
Reviewed-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Andy Gross <agross@codeaurora.org>
Signed-off-by: Olof Johansson <olof@lixom.net>