msm: adsprpc: Add checks to avoid buffer overflow

Do integer overflow check on the length of buffer
to be copied before copying to the buffer.

Change-Id: I425861170125fb3069739af84975c4893462624e
Acked-by: Chenna Kesava Raju <chennak@qti.qualcomm.com>
Signed-off-by: Jeya R <jeyr@codeaurora.org&gt;`>