LU-5639 lnet: portal spreading rotor should be unsigned

LU-5639 lnet: portal spreading rotor should be unsigned

Portal spreading rotor should be unsigned, otherwise lnet may get
negative CPT number and access invalid addresses.

Signed-off-by: Liang Zhen <liang.zhen@intel.com>
Change-Id: Id7f40da241af3b01483fdedd366b09329f530163
Reviewed-on: http://review.whamcloud.com/11936
Reviewed-by: Amir Shehata <amir.shehata@intel.com>
Tested-by: Maloo <hpdd-maloo@intel.com>
Tested-by: Jenkins
Reviewed-by: Isaac Huang <he.huang@intel.com>
Reviewed-by: Doug Oucharek <doug.s.oucharek@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>