Add NXP source files to tf-coverity coverage exclusion list

Several files specific to NXP platforms cannot be compiled with any
build flags at this moment due to external dependencies

Signed-off-by: Madhukar Pappireddy <madhukar.pappireddy@arm.com>
Change-Id: I626fdef608772998125bbb4a20f073566ae051dc
1 file changed