RDMA/bnxt_re: Fix RQE posting logic

This patch adds code to ring RQ Doorbell aggressively
so that the adapter can DMA RQ buffers sooner, instead
of DMA all WQEs in the post_recv WR list together at the
end of the post_recv verb.
Also use spinlock to serialize RQ posting

Signed-off-by: Kalesh AP <kalesh-anakkur.purayil@broadcom.com>
Signed-off-by: Devesh Sharma <devesh.sharma@broadcom.com>
Signed-off-by: Selvin Xavier <selvin.xavier@broadcom.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

drivers/infiniband/hw/bnxt_re/bnxt_re.h

@@ -58,6 +58,8 @@
 
 #define BNXT_RE_UD_QP_HW_STALL		0x400000
 
+#define BNXT_RE_RQ_WQE_THRESHOLD	32
+
 struct bnxt_re_work {
 	struct work_struct	work;
 	unsigned long		event;