ksmbd: add support for surrogate pair conversion

ksmbd is missing supporting to convert filename included surrogate pair
characters. It triggers a "file or folder does not exist" error in
Windows client.

[Steps to Reproduce for bug]
1. Create surrogate pair file
touch $(echo -e '\xf0\x9d\x9f\xa3')
touch $(echo -e '\xf0\x9d\x9f\xa4')

2. Try to open these files in ksmbd share through Windows client.

This patch update unicode functions not to consider about surrogate pair
(and IVS).

Reviewed-by: Marios Makassikis <mmakassikis@freebox.fr>
Tested-by: Marios Makassikis <mmakassikis@freebox.fr>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

fs/smb: Swing unicode common code from smb->NLS

Swing most of the inline functions and unicode tables into nls
from the copy in smb/server. This is UCS-2 rather than most
of the rest of the code in NLS, but it currently seems like the
best place for it.

The actual unicode.c implementations vary much more between server
and client so they're unmoved.

Signed-off-by: Dr. David Alan Gilbert <linux@treblig.org>
Reviewed-by: Dave Kleikamp <dave.kleikamp@oracle.com>
Signed-off-by: Steve French <stfrench@microsoft.com>

smb: move client and server files to common directory fs/smb

Move CIFS/SMB3 related client and server files (cifs.ko and ksmbd.ko
and helper modules) to new fs/smb subdirectory:

fs/cifs --> fs/smb/client
fs/ksmbd --> fs/smb/server
fs/smbfs_common --> fs/smb/common

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>