BACKPORT: msm: adsprpc: Use unsigned integer for length values

As the length datatype is signed, an attacker can both overflow
the calculation or supply a negative number to trick the check
into returning an chosen chunk. This can have undesired
consequences. Always use unsigned integer types for length
values.

Change-Id: Ifde2f0d35129014b976507f7723a319c53fabddf
Acked-by: Thyagarajan Venkatanarayanan <venkatan@qti.qualcomm.com>
Signed-off-by: Tharun Kumar Merugu <mtharu@codeaurora.org>
Bug: 63165135
CRs-Fixed: 2139538
Signed-off-by: Dennis Cagle <dcagle@codeaurora.org>
(cherry picked from commit c29e11c774b3c59660c1c599b73b7fabf1492d43)
Signed-off-by: David Lin <dtwlin@google.com>
(cherry picked from commit 157a921e39321002220e040ef8a07dce8e0eccbf)