perf vendor events arm64: Add JSON metrics for Yitian 710 DDR

Add JSON metrics for T-HEAD Yitian 710 SoC DDR.

Reviewed-by: John Garry <[e-mail]>
Signed-off-by: Jing Zhang <[e-mail]>
Acked-by: Ian Rogers <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Shuai Xue <[e-mail]>
Cc: Will Deacon <[e-mail]>
Cc: Zhuo Song <[e-mail]>
Cc: [e-mail]
Cc: [e-mail]
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/pmu-events/arch/arm64/freescale/yitian710/sys/metrics.json

···
+[
+	{
+		"MetricName": "ddr_read_bandwidth.all",
+		"BriefDescription": "The ddr read bandwidth(MB/s).",
+		"MetricGroup": "ali_drw",
+		"MetricExpr": "hif_rd * 64 / 1e6 / duration_time",
+		"ScaleUnit": "1MB/s",
+		"Unit": "ali_drw",
+		"Compat": "ali_drw_pmu"
+	},
+	{
+		"MetricName": "ddr_write_bandwidth.all",
+		"BriefDescription": "The ddr write bandwidth(MB/s).",
+		"MetricGroup": "ali_drw",
+		"MetricExpr": "(hif_wr + hif_rmw) * 64 / 1e6 / duration_time",
+		"ScaleUnit": "1MB/s",
+		"Unit": "ali_drw",
+		"Compat": "ali_drw_pmu"
+	}
+]