net/bnxt: add ring group alloc/free

net/bnxt: add ring group alloc/free

Add HWRM API for ring group alloc/free functions, associated structs and
definitions.
This API allocates and does basic preparation for a ring group in ASIC.
A ring group is identified by an index. It consists of Rx ring id,
completion ring id and a statistics context.

New HWRM calls:
bnxt_hwrm_ring_grp_alloc
	Allocates and does basic preparation for a ring group
bnxt_hwrm_ring_grp_free
	Frees and does cleanup resources of a ring group

Signed-off-by: Ajit Khaparde <ajit.khaparde@broadcom.com>
Signed-off-by: Stephen Hurd <stephen.hurd@broadcom.com>
Reviewed-by: David Christensen <david.christensen@broadcom.com>