qed: Fix next-ptr chains for BE / 32-bit

Commit a91eb52a ("qed: Revisit chain implementation") contains an
incorrect implementation for BE platforms, as device's regpairs containing
addresses are LE and they're not converted correctly when read back.
In addition, it raises a compilation warning for 32-bit platforms where
dma_addr_t is a 32-bit variable.

Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Yuval Mintz <Yuval.Mintz@qlogic.com>
Signed-off-by: David S. Miller <davem@davemloft.net>