NTB: ntb_hw_intel: use local variable pdev

Clean up duplicated expression by replacing it with the equivalent local
variable pdev.

Signed-off-by: Allen Hubbe <Allen.Hubbe@emc.com>
Acked-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Jon Mason <jdmason@kudzu.us>