[media]: refactoring AudioSystem.cpp to C++ style, part 2

* get rid of C style casting, static_cast, reinterpret_cast
and const_cast should be used instead.

Test: m

Change-Id: Ie4161bb9376ec6aabc45a5348226bbecf30ab775
Signed-off-by: Anton Utkin <avutkin@sberdevices.ru>