Fix build error

Error message: frameworks/native/libs/binder/tests/binderRpcTest.cpp:1171:29:
error: comparison of integers of different signs: 'socklen_t' (aka 'int') and 'unsigned int' [-Werror,-Wsign-compare]

Test Report:
Build pass with the following command
source build/envsetup.sh; lunch gambit-trunk_food-userdebug; m vts;

Bug: b/351059357

Change-Id: Ifdf72342f3683ea4b417507157c037e12cf4c937