The following fixes are to be done to increase the code quality:

• avoid implicit casting by using matching types or casting when it is safe. If it is not always safe, use a conversion function to dynamically check that the origin value can fit in the destination type
• add parenthesis for better readability of some expressions
• check the returning value of functions
• add const keyword when mutability is not required
• remove bitfields
• expose and address an Arm GNU Compiler bug regarding the cmse_nonsecure_caller intrinsic
• cast unused parameters/values to void to be more explicit
• add parenthesis around macro parameters
• encapsulate function-like macros into a function to avoid name clashes
• initialise unitialised variables

This fix can first mainly focus on the core components of TF-M (without tests, NS app and platform code).