cifs: Rename struct reparse_posix_data to reparse_nfs_data_buffer and move to common/smb2pdu.h

Function parse_reparse_posix() parses NFS-style reparse points, which are
used only by Windows NFS server since Windows Server 2012 version. This
style is not understood by Microsoft POSIX/Interix/SFU/SUA subsystems.

So make it clear that parse_reparse_posix() function and reparse_posix_data
structure are not POSIX general, but rather NFS specific.

All reparse buffer structures are defined in common/smb2pdu.h and have
_buffer suffix. So move struct reparse_posix_data from client/cifspdu.h to
common/smb2pdu.h and rename it to reparse_nfs_data_buffer for consistency.
Note that also SMB specification in [MS-FSCC] document, section 2.1.2.6
defines it under name "Network File System (NFS) Reparse Data Buffer".
So use this name for consistency.

Having this structure in common/smb2pdu.h can be useful for ksmbd server
code as NFS-style reparse points is the preferred way for implementing
support for special files.

Signed-off-by: Pali Rohár <pali@kernel.org>
Acked-by: Paulo Alcantara (Red Hat) <pc@manguebit.com>
Reviewed-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>