[TF-A] Function parameter should not be modified.

Hello,

In the file common/bl_common.c and other related files, there are instances where function parameters are being modified. This leads to violations when running the Coverity MISRA-C analysis for the ZynqMP platform. To address this issue a new variable is declared and used to store the value from the argument in the code. Is it possible to fix by taking a new variable? Please provide your suggestions.

Regards, Nithin G