MPY_TOOL_LONGINT_IMPL not set correctly in some ports

[jepler]

While reviewing

• Add enable long integer flags to Broadcom #5774
  I noticed that MPY_TOOL_LONGINT_IMPL is not being set correctly, because it depends on the value of LONGINT_IMPL being set earlier in the file.

The problem is that the setting of LONGINT_IMPL is after it use in the ifeq lines. This means LONGINT_IMPL is treated as empty at line 5, 9, and 13 and so none of the -mlongint-impl lines are taken.

The consequence of this is that if there are frozen files (there aren't, in these ports) and they use long ints it won't work.