Add support for original fallocate

In many cases the simple fallocate call is
a no op (since the file is already not sparse) or
can simply be converted from a sparse to a non-sparse
file if we are fallocating the whole file and keeping
the size.

Signed-off-by: Steven French <smfrench@gmail.com>

diff --cc fs/cifs/smb2ops.c
Simple merge