move stdio fd handle checking in fd_determine_type_rights to ensure type is properly set before return

[SneezingCactus]

Before this change, fd_determine_type_rights would return early upon dealing with a stdio file handle without giving it any type (therefore being left as a __WASI_FILETYPE_UNKNOWN). This would end up having repercussions on wasi-sdk's implementation of vfprintf, which doesn't register line breaks properly if the file it's writing to (stdout in the case of printf) isn't a tty, which is mainly checked by seeing if the file is a CHARACTER_DEVICE.