config/qa-checks: Introduce cppcheck and solve cppcheck failures

Update qa-checks_config.yml to include cppcheck on C source files
and solve failures in cppcheck.

Issue-Id: SCM-4882
Signed-off-by: Robbie Cao <robbie.cao@arm.com>
Signed-off-by: Jiacheng Tang <jiacheng.tang@arm.com>
Change-Id: Ic6a56a09e5c55aeee251bfbafb1b1c5bee778ea4