net_sched: psched_ratecfg_precompute() improvements

Before allowing 64bits bytes rates, refactor
psched_ratecfg_precompute() to get better comments
and increased accuracy.

rate_bps field is renamed to rate_bytes_ps, as we only
have to worry about bytes per second.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Ben Greear <greearb@candelatech.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
index df56760..6eab6336 100644
--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h
@@ -680,7 +680,7 @@
 #endif
 
 struct psched_ratecfg {
-	u64	rate_bps;
+	u64	rate_bytes_ps; /* bytes per second */
 	u32	mult;
 	u16	overhead;
 	u8	shift;
@@ -698,7 +698,7 @@
 					  const struct psched_ratecfg *r)
 {
 	memset(res, 0, sizeof(*res));
-	res->rate = r->rate_bps >> 3;
+	res->rate = r->rate_bytes_ps;
 	res->overhead = r->overhead;
 }