NFSv4: Extend fattr bitmaps to support all 3 words

The fattr handling bitmap code only uses the first two fattr words sofar. This
patch adds the 3rd word to being sent but doesn't populate it yet.

Signed-off-by: Miguel Rodel Felipe <Rodel_FM@dsi.a-star.edu.sg>
Signed-off-by: Phua Eu Gene <PHUA_Eu_Gene@dsi.a-star.edu.sg>
Signed-off-by: Khin Mi Mi Aung <Mi_Mi_AUNG@dsi.a-star.edu.sg>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>