Add validation on attr type and size in a2dp_api.cc

Bug: 263958603
Test: atest net_test_stack_a2dp_native
Ignore-AOSP-First: security
Tag: #security

Merged-In: I938467ca4f4b130cd8b4c544096127e679391c06
Change-Id: I938467ca4f4b130cd8b4c544096127e679391c06
(cherry picked from commit 4832e302)