LU-4614 llite: remove lustre_generic_file_{read,write}

LU-4614 llite: remove lustre_generic_file_{read,write}

It looks like lustre_generic_file_{read,write} are a holdover from
2.6.19 where generic_file_aio_read() replaced generic_file_readv()
and cross-kernel interoperability was required for some period of
time. Lustre has since removed support for those older kernels, but
it looks like the wrappers were not deleted at that time. This patch
will delete them.

Pass &iocb->ki_pos as the last argument for these functions instead
of crw_pos, since this is the convention for other callers.  Verify
that this is the same as the current crw_pos argument.  This code can
likely be cleaned up further in a later patch.

Signed-off-by: Jinshan Xiong <jinshan.xiong@intel.com>
Change-Id: Id19edacf93ee2538634feb95580ab885f6069ee7
Reviewed-on: http://review.whamcloud.com/9230
Tested-by: Jenkins
Tested-by: Maloo <hpdd-maloo@intel.com>
Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: Bobi Jam <bobijam@gmail.com>
Reviewed-by: Yang Sheng <yang.sheng@intel.com>