exofs: file and file_inode operations

implementation of the file_operations and inode_operations for
regular data files.

Most file_operations are generic vfs implementations except:
- exofs_truncate will truncate the OSD object as well
- Generic file_fsync is not good for none_bd devices so open code it
- The default for .flush in Linux is todo nothing so call exofs_fsync
  on the file.

Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>

diff --cc fs/exofs/Kbuild
Simple merge

diff --cc fs/exofs/exofs.h
Simple merge

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

diff --cc fs/exofs/inode.c
Simple merge