[CIFS] Reduce cifs stack space usage

The two cifs functions that used the most stack according
to "make checkstack" have been changed to use less stack.

Thanks to jra and Shaggy for helpful ideas

Signed-off-by: Steve French <sfrench@us.ibm.com>
cc: jra@samba.org
cc: shaggy@us.ibm.com

diff --cc fs/cifs/file.c
Simple merge

diff --cc fs/cifs/smbdes.c
Simple merge