cifs: cleanup smb2ops.c and normalize strings

Fix checkpatch warnings/errors in smb2ops.c except "LONG_LINE". Add missing
linebreaks, indentings, __func__. Remove void-returns, unneeded braces.
Address warnings spotted by checkpatch.

Add SPDX License Header.

Add missing "\n" and capitalize first letter in some cifs_dbg() strings.

Signed-off-by: Christoph Probst <kernel@probst.it>
Signed-off-by: Steve French <stfrench@microsoft.com>
Acked-by: Pavel Shilovsky <pshilov@microsoft.com>