rds: UNDO reverts done for rebase code to compile with Linux 4.1 APIs

rds: UNDO reverts done for rebase code to compile with Linux 4.1 APIs

Commit 163377dd82f2d81809aabe736a2e0ea515055a69 does reverts
to common ancestor of upstream and UEK2 to rebase UEK2 patches
for net/rds. This commit undoes reverts needed to compile to
Linux 4.0 APIs.

UNDO Revert "net: Replace get_cpu_var through this_cpu_ptr" for net/rds
This commit does UNDO of revert of commit 903ceff7ca7b4d80c083a80ee5163b74e9fa359f for net/rds.

UNDO Revert "rds: switch ->inc_copy_to_user() to passing iov_iter"
This commit does UNDO of revert of commit c310e72c89926e06138e4881f21e4c8da3e7ef18

UNDO Revert of "rds: switch rds_message_copy_from_user() to iov_iter"
This commit does UNDO of revert of commit 083735f4b01b703184c0e11c2e384b2c60a8aea4.

UNDO Revert "put iov_iter into msghdr" for net/rds
This commit does UNDO of revert of commit c0371da6047abd261bc483c744dbc7d81a116172 for net/rds

UNDO Revert "net: introduce helper macro for_each_cmsghdr" for net/rds
This commit does UNDO of revert of commit f95b414edb18de59940dcebbefb49cf25c6d505c for net/rds

UNDO Revert "rds: Fix min() warning in rds_message_inc_copy_to_user()"
This commit does UNDO of revert of commit 6ff4a8ad4b6eae5171754fb60418bc81834aa09b.

UNDO Revert "rds: Make rds_message_copy_from_user() return 0 on success."
This commit does UNDO of revert of commit d0a47d32724bf0765b8768086ef1a7a6d074a7a0.

UNDO Revert "net: Remove iocb argument from sendmsg and recvmsg" for net/rds
This commit does UNDO of revert of commit 1b784140474e4fc94281a49e96c67d29df0efbde for net/rds.

These commits were reverted earlier to rebase unmodified UEK2 RDS code
(UNDO needed to compile to new Linux 4.1 kernel APIs - changed *after* Linux 3.18)

Signed-off-by: Mukesh Kacker <mukesh.kacker@oracle.com>