Revert "NFSv4.2: Change the default KConfig value for READ_PLUS"

This reverts commit 7fd461c4.

Unfortunately, it has come to our attention that there is still a bug
somewhere in the READ_PLUS code that can result in nfsroot systems on
ARM to crash during boot.

Let's do the right thing and revert this change so we don't break
people's nfsroot setups.

Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>