avc_utils: check delta_scale range to avoid overflow

In some cases delta_scale can be negative value while lastScale is
defined as size_t which is unsigned. Adding negative value to unsigned
causes overflow which triggers crash because of compiler flags:
LOCAL_SANITIZE := unsigned-integer-overflow signed-integer-overflow

Test: play specific contents
Bug: 62213565

Author: Michal Piechowski <michal.piechowski@sonymobile.com>
Change-Id: I8b3ad12a95f977db56073c078c179290d8d92368
(cherry picked from commit 0dc618869098e67a2b60971b8699bfb8b8a85dc7)