Fix st_mode of . and .. directories in readdirplus

Generally, st_mode (as a field of struct stat) is made of S_IFDIR, S_IFREG, etc., but d_type (as a field of struct dirent) is made of DT_DIR, DT_REG, etc. But these definitions are differ up to a 12 bit shift. It leads to incorrect attributes of . and .. in Windows guest, so fix it.

Fixes https://bugzilla.redhat.com/show_bug.cgi?id=2074311