qed: sanitize PBL chains allocation

PBL chain elements are actually DMA addresses stored in __le64, but
currently their size is hardcoded to 8, and DMA addresses are assigned
via cast to variable-sized dma_addr_t without any bitwise conversions.
Change the type of pbl_virt array to match the actual one, add a new
field to store the size of allocated DMA memory and sanitize elements
assignment.

Misc: give more logic names to the members of qed_chain::pbl_sp embedded
struct.

Signed-off-by: Alexander Lobakin <alobakin@marvell.com>
Signed-off-by: Igor Russkikh <irusskikh@marvell.com>
Signed-off-by: Michal Kalderon <michal.kalderon@marvell.com>
Signed-off-by: David S. Miller <davem@davemloft.net>