LU-9325 msg: replace obsolete simple_strtoul use

LU-9325 msg: replace obsolete simple_strtoul use

The kernel function simple_strtoul() has been superseded by the
kstrto* family of functions. Replace all uses of simple_strto*()
with the equivalent kstrto*() function in the msg subsystem.

Change-Id: I5ca5df29b8b2f34107ee40628ab3b77d57547b99
Signed-off-by: James Simmons <uja.ornl@yahoo.com>
Reviewed-on: https://review.whamcloud.com/33959
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Jenkins
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Ben Evans <bevans@cray.com>
Reviewed-by: Arshad Hussain <arshad.super@gmail.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>