libcamera: utils: Use internal basename implementation.

Differing implementations of basename() exist, some of which may modify
the content of the string passed as an argument.

The implementation of basename() is trivial, thus to support different
C librariese, provide our own version which accepts and returns a const
char *.

Update the call sites to use the new implementation.

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

src/libcamera/include/utils.h

@@ -15,6 +15,8 @@ namespace libcamera {
 
 namespace utils {
 
+const char *basename(const char *path);
+
 /* C++11 doesn't provide std::make_unique */
 template<typename T, typename... Args>
 std::unique_ptr<T> make_unique(Args&&... args)