staging: rtl8712: Removed redundant code from function oid_rt_pro_write_register_hdl

In function oid_rt_pro_write_register_hdl, Adapter->ImrContent is
assigned with RegRWStruct->value but Adapter->ImrContent is never used
anywhere else. So those lines has no impact and are removed removed.

As that was the only place where ImrContent was used, so the member
variable is removed from the structure _adapter

Signed-off-by: Deepak Mishra <linux.dkm@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>