The vfs_clone_file_prep is a generic function to be called by filesystem
implementations only.  Rename the prefix to generic_ and make it more
clear that it applies to remap operations, not just clones.
Signed-off-by: NDarrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: NAmir Goldstein <amir73il@gmail.com>
Signed-off-by: NDave Chinner <david@fromorbit.com>