[MCJIT] Turn the getSymbolAddress free function created in r218626 into a static
member of RTDyldMemoryManager (and rename to getSymbolAddressInProcess).

The functionality this provides is very specific to RTDyldMemoryManager, so it
makes sense to keep it in that class to avoid accidental re-use.

No functional change.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218741 91177308-0d34-0410-b5e6-96231b3b80d8