impi:Remove unneeded setting of module owner to THIS_MODULE in the platform structure, powernv_ipmi_driver

This removes the no longer required setting of the module owner
for the plaform structure,powernv_ipmi_driver to THIS_MODULE as
the driver core for ipmi drivers will directly find and
set the module owner for this driver.
Signed-off-by: Nicholas Krause <xerofoify@gmail.com>
Signed-off-by: Corey Minyard <cminyard@mvista.com>