Fix C++ compilation: cast void* before pointer arithmetic

[sharpeye]

Fixes C++ compilation errors. The code uses pointer arithmetic on void*, which is a GNU C extension that works in C mode but is not allowed in C++.

Error example:

error: arithmetic on a pointer to void
   43 |         hi = *(const volatile uint32_t __force *)(addr + 4);
      |                                                   ~~~~ ^

[birkelund]

It compiles just fined under clang 19, so please be clear in the commit message that this is because the static inline functions use a GNU C extension that is not allowed by default for C++.

I'm more used to void *, but I get the pain due to using the headers from C++, so I'm fine with fixing up the headers here.

[birkelund]

@sharpeye you can ignore the build failure on oracular and checkpatch complaining about volatile, but please add your sign-off ;)

[birkelund]

Merged; Thanks!