eliminate the double copy, and improve cifs write performance and
help the server by upping the typical write size from 4K to 16K
(or even larger if wsize set explicitly)  for servers which support this.
Part 1 of 2
Signed-off-by: NDave Kleikamp <shaggy@austin.ibm.com>
Signed-off-by: NSteve French  <sfrench@us.ibm.com>