cxgb4/cxgb4vf: Add code to calculate T5 BAR2 Offsets for SGE Queue Registers

Add new Common Code facilities for calculating T5 BAR2 Offsets for SGE Queue
Registers. This new code can handle situations where

    Queues Per Page * SGE BAR2 Queue Register Area Size > Page Size

Based on original work by Casey Leedom <leedom@chelsio.com>

Signed-off-by: Hariprasad Shenai <hariprasad@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>