[PATCH v7 1/6] ntdll: Use st_rdev for special devices in get_mountmgr_fs_info.

[Erich E. Hoover]

Overall, this patchset has two objectives:
1) remove the volume information duplication in
dlls/kernelbase/volume.c in preference to the version in
dlls/mountmgr.sys/device.c
2) set the stage for fixing the advertisement of reparse point support
( https://github.com/wine-staging/wine-staging/blob/master/patches/ntdll-Junct...
)

This specific patch addresses an issue uncovered by revising the last
patch to work without FILE_LIST_DIRECTORY.  Without this patch
attempts to query volume information from drive Z:  fail because the
mountmgr does not find the device (st_dev != st_rdev).  Many thanks to
Zeb for her helping track this down.

v7: new patch

Best,
Erich