bnxt_en: Allocate extra QP backing store memory when RoCE FW reports it

The Fast QP modify destroy RoCE feature requires additional QP entries
in QP context backing store. FW reports the extra count to be
allocated during backing store query. Use this value and allocate extra
memory.  Note that this works for both the V1 and V1 backing store
FW APIs.

Signed-off-by: Selvin Xavier <selvin.xavier@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Link: https://lore.kernel.org/r/20231212005122.2401-7-michael.chan@broadcom.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>