bare-arm: Add dummy __assert_func and __fatal_error

Required to build bare-arm with debugging.

Signed-off-by: Sven Wegener <sven.wegener@stealer.net>
stmhal: Replace __WFI with __BKPT in __fatal_error

On a fatal error, bring the processor into debug state.

Signed-off-by: Sven Wegener <sven.wegener@stealer.net>
stmhal: Declare variables in include files

Else we end up with several instances of the variable.

Signed-off-by: Sven Wegener <sven.wegener@stealer.net>