replace opencoded pvfs_bufmap_copy_to_kernel_iovec,
pvfs_bufmap_copy_to_user_iovec, pvfs_bufmap_copy_iovec_from_kernel,
and pvfs_bufmap_copy_iovec_from_user with pvfs_bufmap_copy_to_iovec
and pvfs_bufmap_copy_from_iovec, which both use the iov_iter
interface.
Signed-off-by: NMike Marshall <hubcap@omnibond.com>

  Don't check for negative rc from boolean.

  Don't pointlessly initialize variables, it short-circuits
  gcc's uninitialized variable warnings. And max_new_nr_segs
  can never be zero, so don't check for it.

  Preserve original kstrdup pointer for freeing later.

  Don't check for negative value in unsigned variable.
Signed-off-by: NMike Marshall <hubcap@omnibond.com>

Signed-off-by: NMike Marshall <hubcap@omnibond.com>

Signed-off-by: NMike Marshall <hubcap@omnibond.com>